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

    <documentType>4</documentType><periodOfReport>2003-10-23</periodOfReport><notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001042729</issuerCik>
        <issuerName>MERCANTILE BANK CORP</issuerName>
        <issuerTradingSymbol>MBWM</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001208521</rptOwnerCik>
            <rptOwnerName>JONES SUSAN K</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>SUSAN K. JONES &amp; ASSOCIATES</rptOwnerStreet1>
            <rptOwnerStreet2>251 PLYMOUTH SE</rptOwnerStreet2>
            <rptOwnerCity>E. GRAND RAPIDS</rptOwnerCity>
            <rptOwnerState>MI</rptOwnerState>
            <rptOwnerZipCode>49506</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><derivativeTable><derivativeTransaction><securityTitle><value>Director stock option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>40.45</value></conversionOrExercisePrice><transactionDate><value>2003-10-23</value></transactionDate><deemedExecutionDate></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>500</value></transactionShares><transactionPricePerShare><footnoteId id="F2" /></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2008-10-23</value><footnoteId id="F1" /></exerciseDate><expirationDate><value>2013-10-22</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>500</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>500</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">This director stock option is subject to accelerated vesting in certain circumstances pursuant to the issuer's Independent Director Stock Option Plan.</footnote><footnote id="F2">No price is entered here as this is a director stock option </footnote></footnotes><remarks></remarks><ownerSignature><signatureName>Jerome M. Schwartz,
Attorney-in-fact</signatureName><signatureDate>2003-10-27</signatureDate></ownerSignature></ownershipDocument>

