<SUBMISSION>
<ACCESSION-NUMBER>0000920371-06-000031
<TYPE>3
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20060612
<FILING-DATE>20060620
<DATE-OF-FILING-DATE-CHANGE>20060620
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>SIMPSON MANUFACTURING CO INC /CA/
<CIK>0000920371
<ASSIGNED-SIC>3420
<IRS-NUMBER>943196943
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>4120 DUBLILN BLVD STE 400
<CITY>DUBLIN
<STATE>CA
<ZIP>94568
<PHONE>9255609000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>4120 DUBLIN BLVD STE 400
<CITY>DUBLIN
<STATE>CA
<ZIP>94568
</MAIL-ADDRESS>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>California College of the Arts
<CIK>0001366642
<STATE-OF-INCORPORATION>CA
<FISCAL-YEAR-END>0430
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>3
<ACT>34
<FILE-NUMBER>001-13429
<FILM-NUMBER>06915905
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>5212 BROADWAY
<CITY>OAKLAND
<STATE>CA
<ZIP>95618
<PHONE>510-594-3600
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>5212 BROADWAY
<CITY>OAKLAND
<STATE>CA
<ZIP>95618
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2006-06-12</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000920371</issuerCik>
        <issuerName>SIMPSON MANUFACTURING CO INC /CA/</issuerName>
        <issuerTradingSymbol>NYSE:SSD</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001366642</rptOwnerCik>
            <rptOwnerName>California College of the Arts</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>5212 BROADWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>OAKLAND</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94618</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>(See Note 1 below)</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>57120</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes></footnotes>

    <remarks>Note 1:  Barclay Simpson is a Director, Officer and 10% owner of Simpson Manufacturing Co., Inc. and is a member of the Board of Directors and the Executive Committee of the reporting person.</remarks>

    <ownerSignature>
        <signatureName>David Kirshman</signatureName>
        <signatureDate>2006-06-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
