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

<documentType>4</documentType><periodOfReport>2003-05-08</periodOfReport><notSubjectToSection16>1</notSubjectToSection16>
<issuer><issuerCik>0001065865</issuerCik>
        <issuerName>JANUS CAPITAL GROUP INC</issuerName>
<issuerTradingSymbol>JNS</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001183259</rptOwnerCik>
            <rptOwnerName>BARNES JAMES E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
<reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>1</isOther><otherText>Former Director</otherText></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock, Par Value $0.01</value><footnoteId id="F1"/></securityTitle><transactionDate><value>2001-05-23</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>G</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>87000</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>87000</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>Held by Trust</value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock, Par Value $0.01</value><footnoteId id="F1"/></securityTitle><transactionDate><value>2001-05-23</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>G</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>87000</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>87000</value><footnoteId id="F3"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>Held by Trust</value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><derivativeSecurity><securityTitle><value>Option (Right to Buy) and LSAR</value><footnoteId id="F4"/></securityTitle><conversionOrExercisePrice><value>12.27</value></conversionOrExercisePrice><transactionDate><value>2003-05-08</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>19378</value></transactionShares><transactionValue><value>12.27</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2003-05-09</value></exerciseDate><expirationDate><value>2013-05-07</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>19378</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>19378</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">Transaction previously reported.</footnote><footnote id="F2">87,000 shares are held by the James E. Barnes Revocable Trust, U/A dated March 29, 1998.</footnote><footnote id="F3">87,000 shares are held by the Mary M. Barnes (wife) Revocable Trust, U/A dated March 29, 1998.</footnote><footnote id="F4">Limited Stock Appreciation Rights (&amp;quot;LSARs&amp;quot;) are granted in tandem with stock options.  LSARs are automatically exercised (in lieu of related options) upon change-of-control of the Company which has not been approved by certain members of the Company's board of directors and result in the receipt of only cash by the option holder.  LSARs terminate when the related options are exercised or terminated.</footnote></footnotes><ownerSignature><signatureName>Barbara E. Chesebro, Attorney-in-Fact for James E. Barnes</signatureName><signatureDate>2003-05-12</signatureDate></ownerSignature></ownershipDocument>

