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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 BNXP/H1+/8lM/7x7ZvNT89dLAqvHHLHWADrOzmpL3iluj3jbKBtTlwBtWTziwsWl
 greoLlTC3s4cAIFvvYmDKg==

<SEC-DOCUMENT>0001463556-11-000022.txt : 20110214
<SEC-HEADER>0001463556-11-000022.hdr.sgml : 20110214
<ACCEPTANCE-DATETIME>20110214090301
ACCESSION NUMBER:		0001463556-11-000022
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20110211
FILED AS OF DATE:		20110214
DATE AS OF CHANGE:		20110214

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ARIBA INC
		CENTRAL INDEX KEY:			0001084755
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PREPACKAGED SOFTWARE [7372]
		IRS NUMBER:				770439730
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		807 11TH AVENUE
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94089
		BUSINESS PHONE:		6509306200

	MAIL ADDRESS:	
		STREET 1:		807 11TH AVENUE
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94089

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			COSTELLO KEVIN
		CENTRAL INDEX KEY:			0001183230

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-26299
		FILM NUMBER:		11602342

	MAIL ADDRESS:	
		STREET 1:		C/O ARIBA INC
		STREET 2:		807 11TH AVENUE
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94089
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2011-02-11</periodOfReport>

    <issuer>
        <issuerCik>0001084755</issuerCik>
        <issuerName>ARIBA INC</issuerName>
        <issuerTradingSymbol>ARBA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001183230</rptOwnerCik>
            <rptOwnerName>COSTELLO KEVIN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ARIBA, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>807 11TH AVENUE</rptOwnerStreet2>
            <rptOwnerCity>SUNNYVALE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94089</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2011-02-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>75000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>30.0803</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>180227</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The shares sold in this transaction were part of Mr. Costello's 10b5-1 Plan</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Kevin Costello</signatureName>
        <signatureDate>2011-02-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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