<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-08-09</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000108215</issuerCik>
        <issuerName>WOODHEAD INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>WDHD</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001215754</rptOwnerCik>
            <rptOwnerName>WIEDOR DUANE E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3 PARKWAY NORTH, SUITE 550</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DEERFIELD</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60015</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Woodhead Industries, Inc. Common Stock, $1 Par Value</value>
            </securityTitle>
            <transactionDate>
                <value>2006-08-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>13000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.25</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right-to-buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>16.40</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-08-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.85</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2002-04-24</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2011-04-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $1 Par Value</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right-to-buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>14.83</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-08-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7260</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4.42</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2002-10-25</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2011-10-25</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $1 Par Value</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7260</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right-to-buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>16.05</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-08-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3740</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.20</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2003-01-25</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2012-01-25</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $1 Par Value</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3740</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right-to-buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>10.375</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-08-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.875</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2003-10-31</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2012-10-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $1 Par Value</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right-to-buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>16.46</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-08-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>18000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.79</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2004-10-30</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2013-10-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $1 Par Value</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right-to-buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>13.48</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-08-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>18000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.77</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-09-22</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-09-22</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $1 Par Value</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right-to-buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>12.55</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-08-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>30000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>6.70</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2012-11-25</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $1 Par Value</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>30000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents restricted stock that vested in connection with the Agreement and Plan of Merger dated as of June 30, 2006, by and between Molex, Inc., MLX Acquisition Corporation and Woodhead Industries, Inc. (the &quot;Merger Agreement&quot;). Such shares were disposed of for a cash payment of $19.25 per share, pursuant to the Merger Agreement.</footnote>
        <footnote id="F2">This option, vesting in three equal annual installments beginning on this date, was canceled in the merger in exchange for a cash payment representing the difference between the exercise price of the option and the tender offer price of $19.25 per share, as set forth in the Merger Agreement.</footnote>
        <footnote id="F3">This option was canceled in the merger in exchange for a cash payment representing the difference between the exercise price of the option and the tender offer price of $19.25 per share, as set forth in the Merger Agreement.</footnote>
        <footnote id="F4">This option granted on November 25, 2002, under the terms of the Woodhead Industries, Inc. 2001 Stock Awards Plan, was to vest on the earlier of five years from the grant date, or when the share price closed at or above $20.00 and the average daily share price remained at or above $20.00 for 20 consecutive trading days while the closing price during such period remained above 18.00. This option was canceled in the merger in exchange for a cash payment representing the difference between the exercise price of the option and the tender offer price of $19.25 per share, as set forth in the Merger Agreement.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Robert J. Tortorello for Duane E. Wiedor by Power of Attorney previously filed.</signatureName>
        <signatureDate>2006-08-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2006-08-09
1
0000108215
WOODHEAD INDUSTRIES INC
WDHD
0001215754
WIEDOR DUANE E
3 PARKWAY NORTH, SUITE 550
DEERFIELD
IL
60015
0
1
0
0
Vice President
Woodhead Industries, Inc. Common Stock, $1 Par Value
2006-08-09
4
D
0
13000
19.25
D
0
D
Employee Stock Option (right-to-buy)
16.40
2006-08-09
4
D
0
5000
2.85
D
2002-04-24
2011-04-24
Common Stock, $1 Par Value
5000
0
D
Employee Stock Option (right-to-buy)
14.83
2006-08-09
4
D
0
7260
4.42
D
2002-10-25
2011-10-25
Common Stock, $1 Par Value
7260
0
D
Employee Stock Option (right-to-buy)
16.05
2006-08-09
4
D
0
3740
3.20
D
2003-01-25
2012-01-25
Common Stock, $1 Par Value
3740
0
D
Employee Stock Option (right-to-buy)
10.375
2006-08-09
4
D
0
20000
8.875
D
2003-10-31
2012-10-31
Common Stock, $1 Par Value
20000
0
D
Employee Stock Option (right-to-buy)
16.46
2006-08-09
4
D
0
18000
2.79
D
2004-10-30
2013-10-30
Common Stock, $1 Par Value
18000
0
D
Employee Stock Option (right-to-buy)
13.48
2006-08-09
4
D
0
18000
5.77
D
2005-09-22
2014-09-22
Common Stock, $1 Par Value
18000
0
D
Employee Stock Option (right-to-buy)
12.55
2006-08-09
4
D
0
30000
6.70
D
2012-11-25
Common Stock, $1 Par Value
30000
0
D
Represents restricted stock that vested in connection with the Agreement and Plan of Merger dated as of June 30, 2006, by and between Molex, Inc., MLX Acquisition Corporation and Woodhead Industries, Inc. (the "Merger Agreement"). Such shares were disposed of for a cash payment of $19.25 per share, pursuant to the Merger Agreement.
This option, vesting in three equal annual installments beginning on this date, was canceled in the merger in exchange for a cash payment representing the difference between the exercise price of the option and the tender offer price of $19.25 per share, as set forth in the Merger Agreement.
This option was canceled in the merger in exchange for a cash payment representing the difference between the exercise price of the option and the tender offer price of $19.25 per share, as set forth in the Merger Agreement.
This option granted on November 25, 2002, under the terms of the Woodhead Industries, Inc. 2001 Stock Awards Plan, was to vest on the earlier of five years from the grant date, or when the share price closed at or above $20.00 and the average daily share price remained at or above $20.00 for 20 consecutive trading days while the closing price during such period remained above 18.00. This option was canceled in the merger in exchange for a cash payment representing the difference between the exercise price of the option and the tender offer price of $19.25 per share, as set forth in the Merger Agreement.
/s/ Robert J. Tortorello for Duane E. Wiedor by Power of Attorney previously filed.
2006-08-10