<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-06-27</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000726958</issuerCik>
        <issuerName>CASEYS GENERAL STORES INC</issuerName>
        <issuerTradingSymbol>CASY</issuerTradingSymbol></issuer>
<reportingOwner>
<reportingOwnerId>
            <rptOwnerCik>0000916521</rptOwnerCik>
            <rptOwnerName>LAMBERTI DONALD F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector>
<isOfficer>0</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle></officerTitle>
<otherText></otherText></reportingOwnerRelationship></reportingOwner>
<nonDerivativeSecurity>
<securityTitle>
<value>Common Stock</value></securityTitle>
<transactionDate>
<value>2003-06-27</value></transactionDate>
<deemedExecutionDate>
<value>2003-06-27</value></deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>X</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
<footnoteId id="F1"/></transactionCoding>
<transactionTimeliness>
<value></value></transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>20000</value></transactionShares>
<transactionValue>
<value>10.69</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity>
<nonDerivativeSecurity>
<securityTitle>
<value>Common Stock</value></securityTitle>
<transactionDate>
<value>2003-06-27</value></transactionDate>
<deemedExecutionDate>
<value>2003-06-27</value></deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>X</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
<footnoteId id="F1"/></transactionCoding>
<transactionTimeliness>
<value></value></transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>10000</value></transactionShares>
<transactionValue>
<value>11.74</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity>
<nonDerivativeSecurity>
<securityTitle>
<value>Common Stock</value></securityTitle>
<transactionDate>
<value>2003-06-27</value></transactionDate>
<deemedExecutionDate>
<value>2003-06-27</value></deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>S</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionTimeliness>
<value></value></transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>30000</value></transactionShares>
<transactionValue>
<value>14.11</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>D</value></transactionAcquiredDisposedCode></transactionAmounts>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>3047939</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Option - right to buy</value>
<footnoteId id="F1"/></securityTitle>
<conversionOrExercisePrice>
<value>10.69</value></conversionOrExercisePrice>
<transactionDate>
<value>2003-06-27</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>X</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>20000</value></transactionShares>
<transactionValue>
<value>0.00</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>1996-12-20</value></exerciseDate>
<expirationDate>
<value>2003-07-30</value>
<footnoteId id="F3"/></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>20000</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Option - right to buy</value>
<footnoteId id="F1"/></securityTitle>
<conversionOrExercisePrice>
<value>14.93</value></conversionOrExercisePrice>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>J</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
<footnoteId id="F2"/></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0.00</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>D</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>2000-07-26</value></exerciseDate>
<expirationDate>
<value>2003-07-30</value>
<footnoteId id="F3"/></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>10000</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>10000</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Option - right to buy</value>
<footnoteId id="F1"/></securityTitle>
<conversionOrExercisePrice>
<value>11.74</value></conversionOrExercisePrice>
<transactionDate>
<value>2003-06-27</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>X</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>10000</value></transactionShares>
<transactionValue>
<value>0.00</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>2002-05-24</value></exerciseDate>
<expirationDate>
<value>2003-07-30</value>
<footnoteId id="F3"/></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>10000</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<footnotes>
<footnote id="F1">Pursuant to terms and conditions of 2000 Stock Option Plan (or predecessor plan).</footnote>
<footnote id="F2">No transaction is being reported on this line.</footnote>
<footnote id="F3">Under the 2000 Stock Option Plan, all options expire three months after the date of the option holder&apos;s termination (including retirement) of employment.  Mr. Lamberti retired from his employment by the Company on April 30, 2003.  He remains on the Board of Directors.</footnote></footnotes>
<ownerSignature>
<signatureName>William J. Noth, under power of attorney dated 6/6/03</signatureName>
<signatureDate>2003-07-01</signatureDate></ownerSignature></ownershipDocument>


