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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-02-08</periodOfReport>

    <issuer>
        <issuerCik>0000094673</issuerCik>
        <issuerName>STORAGE TECHNOLOGY CORP</issuerName>
        <issuerTradingSymbol>STK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001316604</rptOwnerCik>
            <rptOwnerName>Zawatski Brenda</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE STORAGETEK DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOUISVILLE</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80028</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP/GM, ILM</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-02-08</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>33315</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.1</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>33315</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>31.79</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-02-08</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>79579</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-02-08</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>79579</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>79579</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This grant has two distinct vesting provisions.  One-fourth of 24,579 shares will vest on each of the first four anniversaries of the date of grant.  The remaining 55,000 shares will vest four years from the date of grant, except that the vesting of one-fourth of the 55,000 shares may be accelerated on each of the first, second and third anniversaries of the date of grant if StorageTek meets predetermined performance criteria, set by the Human Resources and Compensation Committee of the Board of Directors.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Donald H. Kronenberg</signatureName>
        <signatureDate>2005-02-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2005-02-08
0000094673
STORAGE TECHNOLOGY CORP
STK
0001316604
Zawatski Brenda
ONE STORAGETEK DRIVE
LOUISVILLE
CO
80028
0
1
0
0
VP/GM, ILM
Common Stock
2005-02-08
4
A
0
33315
0.1
A
33315
D
Stock Options (Right to buy)
31.79
2005-02-08
4
A
0
79579
0
A
2015-02-08
Common Stock
79579
79579
D
This grant has two distinct vesting provisions.  One-fourth of 24,579 shares will vest on each of the first four anniversaries of the date of grant.  The remaining 55,000 shares will vest four years from the date of grant, except that the vesting of one-fourth of the 55,000 shares may be accelerated on each of the first, second and third anniversaries of the date of grant if StorageTek meets predetermined performance criteria, set by the Human Resources and Compensation Committee of the Board of Directors.
Donald H. Kronenberg
2005-02-10