<SUBMISSION>
<ACCESSION-NUMBER>0000920371-03-000029
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20030606
<FILING-DATE>20030606
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>LAMSON STEPHEN B
<CIK>0001035241
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-13429
<FILM-NUMBER>03736125
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>4120 DUBLIN BLVD
<STREET2>SUITE 400
<CITY>DUBLIN
<STATE>CA
<ZIP>94568
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>4120 DUBLIN BLVD
<STREET2>SUITE 400
<CITY>DUBLIN
<STATE>CA
<ZIP>94568
</MAIL-ADDRESS>
</REPORTING-OWNER>
<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>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-06-06</periodOfReport>
    <issuer>
        <issuerCik>0000920371</issuerCik>
        <issuerName>SIMPSON MANUFACTURING CO INC /CA/</issuerName>
        <issuerTradingSymbol>NYSE:SSD</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001035241</rptOwnerCik>
            <rptOwnerName>LAMSON STEPHEN B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Pres/COO Simpson Strong-Tie Co</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>1988-08-08</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>J</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionAmounts><transactionShares><value>0</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>92904</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>1988-08-08</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>J</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionAmounts><transactionShares><value>0</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>2540</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By Trust</value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><derivativeSecurity><securityTitle><value>Options on Common Stock</value></securityTitle><conversionOrExercisePrice><value>32.9</value></conversionOrExercisePrice><transactionDate><value>2003-06-06</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>6000</value></transactionShares><transactionValue><value>32.9</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2004-01-01</value><footnoteId id="F2"/></exerciseDate><expirationDate><value>2009-12-31</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>6000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>6000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Options on Common Stock</value></securityTitle><conversionOrExercisePrice><value>18.7188</value></conversionOrExercisePrice><transactionDate><value>1988-08-08</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>J</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionAmounts><transactionShares><value>0</value></transactionShares><transactionValue><value>18.7188</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2000-01-01</value><footnoteId id="F2"/></exerciseDate><expirationDate><value>2005-12-31</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>5000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Options on Common Stock</value></securityTitle><conversionOrExercisePrice><value>21.875</value></conversionOrExercisePrice><transactionDate><value>1988-08-08</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>J</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionAmounts><transactionShares><value>0</value></transactionShares><transactionValue><value>21.875</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2001-01-01</value><footnoteId id="F2"/></exerciseDate><expirationDate><value>2006-12-31</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>5000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">Transaction code &amp;quot;J&amp;quot; does not represents a transaction. These lines are reporting securities owned as of the date of this filing.</footnote><footnote id="F2">This date represents the date of the first annual vesting period. This option vests equally over four year beginning with the date of grant.</footnote></footnotes><ownerSignature><signatureName>/s/Stephen B. Lamson</signatureName><signatureDate>2003-06-06</signatureDate></ownerSignature></ownershipDocument>

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</TEXT>
</DOCUMENT>
</SUBMISSION>
