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

    <schemaVersion>X0201</schemaVersion>

    <documentType>4/A</documentType>
    <periodOfReport>2004-01-05</periodOfReport>
    <dateOfOriginalSubmission>2004-01-14</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001085913</issuerCik>
        <issuerName>FARMERS &amp; MERCHANTS BANCORP</issuerName>
        <issuerTradingSymbol>FMCB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>

        <reportingOwnerId>
            <rptOwnerCik>0001159021</rptOwnerCik>
            <rptOwnerName>HALEY STEPHEN W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>P.O.BOX 959</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PEBBLE BEACH</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>93953</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
        <isDirector>0</isDirector>
        <isOfficer>1</isOfficer>
        <isTenPercentOwner>0</isTenPercentOwner>
        <isOther>0</isOther>
        <officerTitle>Executive Vice President</officerTitle>
    </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>

        <securityTitle>
            <value>Common Stock</value>
        </securityTitle>

        <transactionDate>
            <value>2004-01-05</value>
        </transactionDate>
    <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>P</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
    </transactionCoding>
        <transactionAmounts>

            <transactionShares>
                <value>35</value>
            </transactionShares>

            <transactionPricePerShare>
                <value>10500</value>
            </transactionPricePerShare>

            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>

            <sharesOwnedFollowingTransaction>
                <value>85</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>

            <directOrIndirectOwnership>
                <value>D</value>
            </directOrIndirectOwnership>
        </ownershipNature>
        </nonDerivativeTransaction>

    </nonDerivativeTable>
<remarks>THIS AMENDMENT IS TO CORRECT THE TRANSACTION DATE TO 01/05/2004.</remarks>

    <ownerSignature>
        <signatureName>/S/Stephen W. Haley</signatureName>
        <signatureDate>2004-01-15</signatureDate>
    </ownerSignature>

</ownershipDocument>

