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

    <schemaVersion>X0201</schemaVersion>

    <documentType>3/A</documentType>

    <periodOfReport>2001-05-31</periodOfReport>

    <dateOfOriginalSubmission>2001-06-06</dateOfOriginalSubmission>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000885245</issuerCik>
        <issuerName>BUCKLE INC</issuerName>
        <issuerTradingSymbol>BKE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001247713</rptOwnerCik>
            <rptOwnerName>SMITH KARI G</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2407 W 24TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>KEARNEY</rptOwnerCity>
            <rptOwnerState>NE</rptOwnerState>
            <rptOwnerZipCode>68845</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP Sales</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Purchase)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.5833</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2005-01-30</value>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Purchase)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>9.2917</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2007-02-01</value>
                <footnoteId id="F4"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>21600</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Purchase)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.3333</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2006-02-02</value>
                <footnoteId id="F5"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Purchase)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>26.75</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2009-01-29</value>
                <footnoteId id="F7"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Performance based - 100% exercisable as goal was achieved.</footnote>
        <footnote id="F2">Date exercisable was originally incorrectly reported as exercisable: 1) Upon certification that goals have been met - 1/3 immediately, 1/3 on 1/30/1999, and 1/3 on 1/29/2000; or 2) 100% on 12/31/2006.  Date exercisable should have instead been reported as exercisable: 1) Upon certification that goals have been met - 1/3 immediately, 1/3 on 1/30/1999, and 1/3 on 1/29/2000; 2) Upon the fair market value of the common stock of the Company being equal to two times the option price per share; or 3) 100% on 1/2/2007.</footnote>
        <footnote id="F3">Expiration date was originally incorrectly reported as 3/29/2006. It should have instead been reported as 1/30/2005.</footnote>
        <footnote id="F4">Expiration date was originally incorrectly reported as 1/31/2007. It should have instead been reported as 2/1/2007.</footnote>
        <footnote id="F5">Expiration date was originally incorrectly reported as 3/17/2007. It should have instead been reported as 2/2/2006.</footnote>
        <footnote id="F6">Date exercisable was originally incorrectly reported as exercisable: 1) Upon certification that goals have been met - 1/3 immediately, 1/3 on 1/28/2001, and 1/3 on 1/27/2002; or 2) 100% on 12/30/2008.  Date exercisable should have instead been reported as exercisable: 1) Upon certification that goals have been met - 1/3 immediately, 1/3 on 2/3/2001, and 1/3 on 2/2/2002; 2) Upon the fair market value of the common stock of the Company being equal to two times the option price per share; or 3) 100% on 12/30/2008.</footnote>
        <footnote id="F7">Expiration date was originally incorrectly reported as 1/30/2009. It should have instead been reported as 1/29/2009.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Karen B. Rhoads by Power of Attorney</signatureName>
        <signatureDate>2004-02-25</signatureDate>
    </ownerSignature>
</ownershipDocument>

