-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 PLWPs0JOfrl9zMOD2JTMutGC3I/J4EfTO/eXkaF1uTeH0kWdVLXcbW3U0JwYnR+t
 6M0vvri6EVsu4agr2vnrmA==

<SEC-DOCUMENT>0000067472-04-000147.txt : 20041025
<SEC-HEADER>0000067472-04-000147.hdr.sgml : 20041025
<ACCEPTANCE-DATETIME>20041025195929
ACCESSION NUMBER:		0000067472-04-000147
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20041025
FILED AS OF DATE:		20041025
DATE AS OF CHANGE:		20041025

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MOLEX INC
		CENTRAL INDEX KEY:			0000067472
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRONIC CONNECTORS [3678]
		IRS NUMBER:				362369491
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		2222 WELLINGTON CT
		CITY:			LISLE
		STATE:			IL
		ZIP:			60532
		BUSINESS PHONE:		6309694550

	MAIL ADDRESS:	
		STREET 1:		2222 WELLINGTON COURT
		CITY:			LISLE
		STATE:			IL
		ZIP:			60532

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			COLLINS MICHELLE L
		CENTRAL INDEX KEY:			0001057687
		STANDARD INDUSTRIAL CLASSIFICATION:	PLASTICS, MATERIALS, SYNTH RESINS & NONVULCAN ELASTOMERS [2821]
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1031

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-07491
		FILM NUMBER:		041095097

	BUSINESS ADDRESS:	
		STREET 1:		ONE GOLDWATER CREEK DR
		CITY:			SANDPOINT
		STATE:			ID
		ZIP:			83864
		BUSINESS PHONE:		2082632266

	MAIL ADDRESS:	
		STREET 1:		ONE GOLDWATER CREEK DR
		CITY:			SANDPOINT
		STATE:			ID
		ZIP:			83864
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-10-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000067472</issuerCik>
        <issuerName>MOLEX INC</issuerName>
        <issuerTradingSymbol>MOLX MOLXA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001057687</rptOwnerCik>
            <rptOwnerName>COLLINS MICHELLE L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE GOLDWATER CREEK DR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SANDPOINT</rptOwnerCity>
            <rptOwnerState>ID</rptOwnerState>
            <rptOwnerZipCode>83864</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Unit</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-10-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>224.681</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>24.96</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2014-10-25</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-10-25</value>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>224.681</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>878.712</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The phantom stock units were accrued quarterly on the first business day following the 24th of January, April, July and October under The Molex Incorporated Deferred Compensation Plan and are to be settled 100% in cash upon the reporting person's termination from service on the Issuer's Board of Directors.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Michelle L. Collins</signatureName>
        <signatureDate>2004-10-25</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----