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

    <documentType>4</documentType><periodOfReport>2003-12-16</periodOfReport>
    <issuer>
        <issuerCik>0000949953</issuerCik>
        <issuerName>OAK HILL FINANCIAL INC</issuerName>
        <issuerTradingSymbol>OAKF</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000944276</rptOwnerCik>
            <rptOwnerName>STRAWSER NEIL S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10721 WEATHERSTONE CT.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOVELAND</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>45140</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 without Par Value</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>37098</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeHolding><nonDerivativeHolding><securityTitle><value>Common Stock without Par Value</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>24750</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>Shares held in P &amp; S Properties, Inc. Profit Sharing Plan of which Mr. Strawser is the trustee.</value></natureOfOwnership></ownershipNature></nonDerivativeHolding><nonDerivativeHolding><securityTitle><value>Common Stock without Par Value</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>4950</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>Shares held in a trust in which Mr. Strawser has sole voting rights and dispositive power.</value></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable><derivativeTransaction><securityTitle><value>Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>30.46</value></conversionOrExercisePrice><transactionDate><value>2003-12-16</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>1000</value></transactionShares><transactionPricePerShare><value>0</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2004-12-16</value></exerciseDate><expirationDate><value>2013-12-16</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock without Par Value</value></underlyingSecurityTitle><underlyingSecurityShares><value>1000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes/><remarks/><ownerSignature><signatureName>Ron J. Copher, POA</signatureName><signatureDate>2003-12-18</signatureDate></ownerSignature></ownershipDocument>

