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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2013-03-26</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000021535</issuerCik>
        <issuerName>COHU INC</issuerName>
        <issuerTradingSymbol>COHU</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001573333</rptOwnerCik>
            <rptOwnerName>Giarre Lorenzo</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>12367 CROSTHWAITE CIRCLE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>POWAY</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92064</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President, Ismeca</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>35000</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>10.68</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2014-01-22</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2023-01-22</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>43750</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Number of shares include (i) 17,500 Restricted Stock Units (RSUs) (including shares that will be withheld to cover tax obligations) that in the future will be converted on a one-for-one basis into shares of Cohu, Inc. common stock, immediately upon vesting which is scheduled to occur in four annual installments beginning January 22, 2014 (assuming continued employment through each vest date) and (ii) 17,500 Performance Share Units (PSUs) (including shares that will be withheld to cover tax obligations) that may be increased to 35,000 at the discretion of management and that will be converted on a one-for-one basis into shares of Cohu, Inc. common stock upon vesting.  These PSUs will vest only after the achievement of specified performance goals.  Provided such goals are achieved, vesting is scheduled to occur no earlier than three annual installments beginning January 22, 2014 (subject to continued employment through each vest date).</footnote>
        <footnote id="F2">Exercisable as to 1/4 of the shares on the first four anniversary dates following 1/22/2013.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jeffrey D. Jones (Attorney-in-Fact)</signatureName>
        <signatureDate>2013-03-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
