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

    <documentType>5</documentType><periodOfReport>2003-08-31</periodOfReport>
    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0000836157</issuerCik>
        <issuerName>LINDSAY MANUFACTURING CO</issuerName>
        <issuerTradingSymbol>LNN</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001253721</rptOwnerCik>
            <rptOwnerName>MCLNTOSH DAVE</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>9013 PRESERVE BLVD.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>EDEN PRAIRIE</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>55347</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeHolding><securityTitle><value>Common Stock</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>5000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By Trust Account</value></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable><derivativeHolding><securityTitle><value>Option to Purchase</value></securityTitle><conversionOrExercisePrice><value>21.20</value></conversionOrExercisePrice><exerciseDate><value>2003-09-03</value></exerciseDate><expirationDate><value>2012-09-03</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5062</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>5062</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Option to Purchase</value></securityTitle><conversionOrExercisePrice><value>21.20</value></conversionOrExercisePrice><exerciseDate><value>2004-09-03</value></exerciseDate><expirationDate><value>2012-09-03</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5062</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>5062</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Option to Purchase</value></securityTitle><conversionOrExercisePrice><value>21.20</value></conversionOrExercisePrice><exerciseDate><value>2005-09-03</value></exerciseDate><expirationDate><value>2012-09-03</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5062</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>5062</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Option to Purchase</value></securityTitle><conversionOrExercisePrice><value>21.20</value></conversionOrExercisePrice><exerciseDate><value>2006-09-03</value></exerciseDate><expirationDate><value>2012-09-03</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5062</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>5062</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Option to Purchase</value></securityTitle><conversionOrExercisePrice><value>21.20</value></conversionOrExercisePrice><exerciseDate><value>2007-09-03</value></exerciseDate><expirationDate><value>2012-09-03</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5062</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>5062</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding></derivativeTable><footnotes/><remarks/><ownerSignature><signatureName>Bruce Karsk</signatureName><signatureDate>2003-10-15</signatureDate></ownerSignature></ownershipDocument>

