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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-11-27</periodOfReport>

    <issuer>
        <issuerCik>0000783325</issuerCik>
        <issuerName>WISCONSIN ENERGY CORP</issuerName>
        <issuerTradingSymbol>WEC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001278949</rptOwnerCik>
            <rptOwnerName>RAPPE KRISTINE A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>231 WEST MICHIGAN STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MILWAUKEE,</rptOwnerCity>
            <rptOwnerState>WI</rptOwnerState>
            <rptOwnerZipCode>53203</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr. VP, Chief Admin. Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-11-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>28</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>33.78</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8760</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-11-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>34.99</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8753</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-11-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1191</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7562</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6728</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>ERSP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-11-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1198</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F6"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1198</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8064</value>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Certain shares of restricted stock granted in 1999, the award of which was previously reported, vested in 2004 and 2005 pursuant to their terms upon the achievement by WEC of pre-established earnings per share targets.  Due to clerical errors, WEC inadvertantly missed such vesting and never released the shares to the reporting person.  The reported prices represent the fair market value of WEC common stock on the dates in 2004 ($33.78) and 2005 ($34.99) the Compensation Committee of the WEC Board of Directors validated WEC's earnings per share for 2003 and 2004, respectively, that satisfied the earnings per share targets and resulted in the vesting of the shares.</footnote>
        <footnote id="F2">Includes shares acquired pursuant to a dividend reinvestment feature of Wisconsin Energy Corporation's Stock Plus Investment Plan in transactions exempt from Section 16 pursuant to Rule 16a-11.</footnote>
        <footnote id="F3">Upon the release of restricted stock granted to the reporting person on November 27, 2006, the reporting person deferred the receipt of 1,191 shares of common stock and received instead 1,198 phantom stock units (PSU) pursuant to the WEC Executive Deferred Compensation Plan (EDCP).  As a result, the reporting person is reporting the disposition of 1,191 shares of common stock in exhange for 1,198 PSU.  The difference between the number of shares of common stock deferred and the number of PSU received can be attributed to the fact that the fair market value of the restricted stock (which determines tax liability, and therefore, the net number of shares ultimately released to the reporting person) is determined by averaging the low and high trading prices of WEC common stock on the date of vesting while, pursuant to the terms of the EDCP, the acquisition price of the PSU is equal to the closing price of WEC common stock on the date of acquisition.</footnote>
        <footnote id="F4">Includes shares acquired under Wisconsin Energy Corporation's Employee Retirement Savings Plan (ERSP) in transactions exempt from Section 16(b) pursuant to Rule 16b-3(c) and exempt from reporting pursuant to Rule 16a-3(f)(1)(i)(B).  The number of shares in the ERSP attributable to any one participant varies with the price of the Common Stock.  The information in this report is based on a plan statement dated as of October 31, 2006.</footnote>
        <footnote id="F5">One-for-one.</footnote>
        <footnote id="F6">These phantom stock units were accrued under the EDCP and are to be settled following the reporting person's retirement or other termination of employment.</footnote>
        <footnote id="F7">Includes PSU accrued pursuant to a dividend reinvestment feature of the EDCP in transactions exempt from Section 16 pursuant to Rule 16a-11.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>\s\ Joshua M. Erickson, as Attorney-in-Fact</signatureName>
        <signatureDate>2006-11-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2006-11-27
0000783325
WISCONSIN ENERGY CORP
WEC
0001278949
RAPPE KRISTINE A
231 WEST MICHIGAN STREET
MILWAUKEE,
WI
53203
0
1
0
0
Sr. VP, Chief Admin. Officer
Common Stock
2006-11-27
4
F
0
28
33.78
D
8760
D
Common Stock
2006-11-27
4
F
0
7
34.99
D
8753
D
Common Stock
2006-11-27
4
D
0
1191
D
7562
D
Common Stock
6728
I
ERSP
Phantom Stock Units
2006-11-27
4
A
0
1198
A
Common Stock
1198
8064
D
Certain shares of restricted stock granted in 1999, the award of which was previously reported, vested in 2004 and 2005 pursuant to their terms upon the achievement by WEC of pre-established earnings per share targets.  Due to clerical errors, WEC inadvertantly missed such vesting and never released the shares to the reporting person.  The reported prices represent the fair market value of WEC common stock on the dates in 2004 ($33.78) and 2005 ($34.99) the Compensation Committee of the WEC Board of Directors validated WEC's earnings per share for 2003 and 2004, respectively, that satisfied the earnings per share targets and resulted in the vesting of the shares.
Includes shares acquired pursuant to a dividend reinvestment feature of Wisconsin Energy Corporation's Stock Plus Investment Plan in transactions exempt from Section 16 pursuant to Rule 16a-11.
Upon the release of restricted stock granted to the reporting person on November 27, 2006, the reporting person deferred the receipt of 1,191 shares of common stock and received instead 1,198 phantom stock units (PSU) pursuant to the WEC Executive Deferred Compensation Plan (EDCP).  As a result, the reporting person is reporting the disposition of 1,191 shares of common stock in exhange for 1,198 PSU.  The difference between the number of shares of common stock deferred and the number of PSU received can be attributed to the fact that the fair market value of the restricted stock (which determines tax liability, and therefore, the net number of shares ultimately released to the reporting person) is determined by averaging the low and high trading prices of WEC common stock on the date of vesting while, pursuant to the terms of the EDCP, the acquisition price of the PSU is equal to the closing price of WEC common stock on the date of acquisition.
Includes shares acquired under Wisconsin Energy Corporation's Employee Retirement Savings Plan (ERSP) in transactions exempt from Section 16(b) pursuant to Rule 16b-3(c) and exempt from reporting pursuant to Rule 16a-3(f)(1)(i)(B).  The number of shares in the ERSP attributable to any one participant varies with the price of the Common Stock.  The information in this report is based on a plan statement dated as of October 31, 2006.
One-for-one.
These phantom stock units were accrued under the EDCP and are to be settled following the reporting person's retirement or other termination of employment.
Includes PSU accrued pursuant to a dividend reinvestment feature of the EDCP in transactions exempt from Section 16 pursuant to Rule 16a-11.
\s\ Joshua M. Erickson, as Attorney-in-Fact
2006-11-29