<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4/A</documentType><periodOfReport>2003-07-24</periodOfReport><dateOfOriginalSubmission>2003-07-24</dateOfOriginalSubmission>
    <issuer>
        <issuerCik>0001008554</issuerCik>
        <issuerName>HUMBOLDT BANCORP</issuerName>
        <issuerTradingSymbol>HBEK</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001177441</rptOwnerCik>
            <rptOwnerName>FRANCIS MARK A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O  HUMBOLDT BANCORP</rptOwnerStreet1>
            <rptOwnerStreet2>2998 DOUGLAS BLVD., SUITE 330</rptOwnerStreet2>
            <rptOwnerCity>ROSEVILLE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>95661</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>EVP/Commercial Banking</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-24</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>2000</value></transactionShares><transactionPricePerShare><footnoteId id="F1"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>2000</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeTransaction></nonDerivativeTable><footnotes><footnote id="F1">Detail of Common Stock Owned: 2,000 held Direct, 2,579 held Indirect by Spouse, 1,594 held Direct, 2,584 held Indirect by Spouse 401 K, 1,000  held Indirect by Spouse (Restricted Stock Award Granted to Spouse who is Employed By Humboldt Bancorp on 7/24/03)</footnote></footnotes><remarks/><ownerSignature><signatureName>Mark A. Francis</signatureName><signatureDate>2003-08-04</signatureDate></ownerSignature><ownerSignature><signatureName>Signed by Patrick J. Rusnak, Power of Attorney on File</signatureName><signatureDate>2003-08-04</signatureDate></ownerSignature></ownershipDocument>

