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

    <documentType>3</documentType><periodOfReport>2003-07-30</periodOfReport>
    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001008554</issuerCik>
        <issuerName>HUMBOLDT BANCORP</issuerName>
        <issuerTradingSymbol>HBEK</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001258128</rptOwnerCik>
            <rptOwnerName>PIGEON RONALD B</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>SVP/Controller</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeHolding><securityTitle><value>Common Stock </value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>2000</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><footnotes><footnote id="F1">Restricted Stock Award to vest as follows:                                                                                                         500 - 7/30/2004, 500 - 7/30/2005, 500 - 7/30/2006, 500 - 7/30/2007.</footnote></footnotes><remarks/><ownerSignature><signatureName>Ronald B. Pigeon</signatureName><signatureDate>2003-08-05</signatureDate></ownerSignature></ownershipDocument>

