<SUBMISSION>
<ACCESSION-NUMBER>0001188112-12-002685
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20120821
<FILING-DATE>20120823
<DATE-OF-FILING-DATE-CHANGE>20120823
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>Snead Richard
<CIK>0001539800
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-26396
<FILM-NUMBER>121052277
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>C/O BENIHANA INC.,
<STREET2>8750 NW 36TH STREET, SUITE 300
<CITY>DORAL
<STATE>FL
<ZIP>33178
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>BENIHANA INC
<CIK>0000935226
<ASSIGNED-SIC>5812
<IRS-NUMBER>650538630
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>0330
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>8685 NW 53RD TERRACE
<CITY>MIAMI
<STATE>FL
<ZIP>33166
<PHONE>3055930770
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>8685 NW 53RD TERRACE
<CITY>MIAMI
<STATE>FL
<ZIP>33166
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-08-21</periodOfReport>

    <issuer>
        <issuerCik>0000935226</issuerCik>
        <issuerName>BENIHANA INC</issuerName>
        <issuerTradingSymbol>BNHN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001539800</rptOwnerCik>
            <rptOwnerName>Snead Richard</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BENIHANA INC. 8750 NW 36TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DORAL,</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33178</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Option to buy</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.12</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2012-08-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.18</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2012-07-10</value>
            </exerciseDate>
            <expirationDate>
                <value>2022-01-10</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                    <footnoteId id="F1"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">One-third exercisable 7/10/2012; one-third exercisable 1/10/2013; one-third exercisable 1/10/2014.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Richard Snead</signatureName>
        <signatureDate>2012-08-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
