-----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,
 WwyAPfubotvd2bi8Gjlc4iHOa+XAOpYuvon34Cat+SCsAoKVGbWjQ5s4G5CjyYPE
 WcUGXxFAq7+ns3gmz5EI8g==

<SEC-DOCUMENT>0000067472-05-000072.txt : 20050726
<SEC-HEADER>0000067472-05-000072.hdr.sgml : 20050726
<ACCEPTANCE-DATETIME>20050726084445
ACCESSION NUMBER:		0000067472-05-000072
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050725
FILED AS OF DATE:		20050726
DATE AS OF CHANGE:		20050726

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:			JANNOTTA EDGAR D
		CENTRAL INDEX KEY:			0001012917
		STATE OF INCORPORATION:			IL
		FISCAL YEAR END:			0531

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-07491
		FILM NUMBER:		05972837

	BUSINESS ADDRESS:	
		STREET 1:		WILLIAM BLAIR & COMPANY LLC
		STREET 2:		2222 WEST ADAMS
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60606
		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>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-07-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001012917</rptOwnerCik>
            <rptOwnerName>JANNOTTA EDGAR D</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>2005-07-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>713.245</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>28.46</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-07-25</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-07-25</value>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>713.245</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>36161.821</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">1-1.</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>Edgar D. Jannotta</signatureName>
        <signatureDate>2005-07-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----