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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-01-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000723458</issuerCik>
        <issuerName>STATE BANCORP INC</issuerName>
        <issuerTradingSymbol>stbc</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001204241</rptOwnerCik>
            <rptOwnerName>LASHLEY RICHARD J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O STATE BANCORP, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>2 JERICHO PLAZA</rptOwnerStreet2>
            <rptOwnerCity>JERICHO</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>11753</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>State Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-01-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>375</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1375</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>State Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>205130</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Financial Edge Fund, L.P.</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>State Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>91590</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Financial Edge-Strategic Fund, L.P.</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>State Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>71187</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By PL Capital/Focused Fund, L.P.</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>State Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>94481</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Goodbody/PL Capital, L.P.</value>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>State Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>30709</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Red Rose Trading Estonia OU</value>
                    <footnoteId id="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Amount of shares awarded to Mr. Lashley effective January 2, 2010 under the 2008 Non-Employee Directors Stock Plan in recognition of his service as a Director during 2009.</footnote>
        <footnote id="F2">Total includes 375 shares of stock awarded to Mr. Lashley effective January 2, 2010 under the 2008 Non-Employee Directors Stock Plan in recognition of his service as a Director during 2009.</footnote>
        <footnote id="F3">Financial Edge Fund, L.P. is a Delaware limited partnership.  PL Capital, LLC is a Delaware limited liability company and is the sole General Partner of Financial Edge Fund, L.P.  Mr. Lashley is the holder of a 50% equity interest in, and one of two Managing Members of PL Capital, LLC.  Mr. Lashley disclaims beneficial ownership of the reported securities except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F4">Financial Edge-Strategic Fund, L.P. is a Delaware limited partnership.  PL Capital, LLC is a Delaware limited liability company and is the sole General Partner of Financial Edge-Strategic Fund, L.P.  Mr. Lashley is the holder of a 50% equity interest in, and one of two Managing Members of PL Capital, LLC.  Mr. Lashley disclaims beneficial ownership of the reported securities except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F5">PL Capital/Focused Fund, L.P. is a Delaware limited partnership.  PL Capital, LLC is a Delaware limited liability company and is the sole General Partner of PL Capital/Focused Fund, L.P.  Mr. Lashley is the holder of a 50% equity interest in, and one of two Managing Members of PL Capital, LLC.  Mr. Lashley disclaims beneficial ownership of the reported securities except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F6">Goodbody/PL Capital, L.P. is a Delaware limited partnership.  Goodbody/PL Capital, LLC is a Delaware limited liability company and the sole General Partner of Goodbody/PL Capital, L.P.  Mr. Lashley is the holder of a 50% equity interest in, and one of two Managing Members of Goodbody/PL Capital, LLC.  Mr. Lashley disclaims beneficial ownership of the reported securities except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F7">Red Rose Trading Estonia OU is an Estonian company.  PL Capital, LLC is a Delaware limited liability company and an investment advisor to Red Rose Trading Estonia OU.  Mr. Lashley is the holder of a 50% equity interest in, and one of two Managing Members of, PL Capital, LLC.  Mr. Lashley disclaims beneficial ownership of the reported securities except to the extent of his pecuniary interest therein.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ricahrd J. Lashley</signatureName>
        <signatureDate>2010-01-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
