-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 BAEKCuMIY+M1rfGGhMGxk4o2C+VxdNyv4Et8Jz0GCQGQ2Qvv2bd5lIzVjJOPWX91
 UAyLFj2O6fGjSgn/XGoNmA==

<SEC-DOCUMENT>0001012926-03-000003.txt : 20030729
<SEC-HEADER>0001012926-03-000003.hdr.sgml : 20030729
<ACCEPTANCE-DATETIME>20030729122707
ACCESSION NUMBER:		0001012926-03-000003
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030725
FILED AS OF DATE:		20030729

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:			POTTER ROBERT J
		CENTRAL INDEX KEY:			0001012926
		STATE OF INCORPORATION:			IL
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-07491
		FILM NUMBER:		03807770

	BUSINESS ADDRESS:	
		STREET 1:		2222 WELLINGTON COURT
		STREET 2:		MOLEX INC
		CITY:			LISLE
		STATE:			IL
		ZIP:			60532
		BUSINESS PHONE:		6305274598

	MAIL ADDRESS:	
		STREET 1:		MOLEX INC
		STREET 2:		2222 WELLINGTON COURT
		CITY:			LISLE
		STATE:			IL
		ZIP:			60532
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2003-07-25</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001012926</rptOwnerCik>
            <rptOwnerName>POTTER ROBERT J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>MOLEX INC</rptOwnerStreet1>
            <rptOwnerStreet2>2222 WELLINGTON COURT</rptOwnerStreet2>
            <rptOwnerCity>LISLE</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60532</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>2003-07-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>39.369</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>27.94</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2003-07-25</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2003-07-25</value>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>39.369</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>34611.808</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>

    </derivativeTable>

    <footnotes>
        <footnote id="F1">1 for 1</footnote>
        <footnote id="F2">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>Robert J. Potter</signatureName>
        <signatureDate>2003-07-29</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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