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

    <documentType>4/A</documentType><periodOfReport>2003-09-30</periodOfReport><dateOfOriginalSubmission>2003-09-30</dateOfOriginalSubmission>
    <issuer>
        <issuerCik>0001008554</issuerCik>
        <issuerName>HUMBOLDT BANCORP</issuerName>
        <issuerTradingSymbol>HBEK</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001102044</rptOwnerCik>
            <rptOwnerName>WINZLER JOHN R</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>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><derivativeTable><derivativeTransaction><securityTitle><value>Deferred Rights</value></securityTitle><conversionOrExercisePrice><value>0</value><footnoteId id="F1"/></conversionOrExercisePrice><transactionDate><value>2003-09-30</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>228</value><footnoteId id="F2"/></transactionShares><transactionPricePerShare><value>15.45</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1988-08-08</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>1988-08-08</value><footnoteId id="F1"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock </value></underlyingSecurityTitle><underlyingSecurityShares><value>228</value><footnoteId id="F2"/></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>19381</value><footnoteId id="F3"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">Represents the reporting person's director's fee under Humboldt Bancorp's deferred compensation plan. Under the plan, the director has the right to defer their director's fee to be paid in common stock upon resignation or retirement. The conversion price of the derivative security is 1 for 1, the number of shares purchased for the month are based on the closing price on the last trade date of the month for which the director fees are paid. </footnote><footnote id="F2">Adjusted for Cash Dividend paid September 22, 03, $0.03/Share (38 shares issued). The net of 191 are the shares purchased through the deferral plan for September 2003. </footnote><footnote id="F3">August Director fee miscalculated should have been $4,750 vs. $1,800, due to this error the total shares defferred for August changed from 121 to 319, changing all of the calculations including the Total Beneficial Ownership from 19,182 to 19,381. </footnote></footnotes><remarks/><ownerSignature><signatureName>John R. Winzler</signatureName><signatureDate>2003-11-03</signatureDate></ownerSignature><ownerSignature><signatureName>Signed by Patrick J. Rusnak, Power of Attorney on File</signatureName><signatureDate>2003-11-03</signatureDate></ownerSignature></ownershipDocument>

