-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 ImRQcM0wxvLneoFKbYS2arFDT7/kRwVzLFFd5naQToZZmp2Cx6/o73+dEELK0DF9
 KUN5A6MkupdxErFNrN2lJw==

<SEC-DOCUMENT>0001187824-04-000005.txt : 20041027
<SEC-HEADER>0001187824-04-000005.hdr.sgml : 20041027
<ACCEPTANCE-DATETIME>20041027143112
ACCESSION NUMBER:		0001187824-04-000005
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20041026
FILED AS OF DATE:		20041027
DATE AS OF CHANGE:		20041027

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			IDEX CORP /DE/
		CENTRAL INDEX KEY:			0000832101
		STANDARD INDUSTRIAL CLASSIFICATION:	PUMPS & PUMPING EQUIPMENT [3561]
		IRS NUMBER:				363555336
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		630 DUNDEE RD STE 400
		CITY:			NORTHBROOK
		STATE:			IL
		ZIP:			60062
		BUSINESS PHONE:		8474987070

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KOOMAN CLINTON L
		CENTRAL INDEX KEY:			0001187824

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-10235
		FILM NUMBER:		041099157

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		847 498 7070

	MAIL ADDRESS:	
		STREET 1:		C/O IDEX CORP
		STREET 2:		630 DUNDEE ROAD
		CITY:			NORTHBROOK
		STATE:			IL
		ZIP:			60062
</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>2004-10-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000832101</issuerCik>
        <issuerName>IDEX CORP /DE/</issuerName>
        <issuerTradingSymbol>IEX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001187824</rptOwnerCik>
            <rptOwnerName>KOOMAN CLINTON L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O IDEX CORP</rptOwnerStreet1>
            <rptOwnerStreet2>630 DUNDEE ROAD</rptOwnerStreet2>
            <rptOwnerCity>NORTHBROOK</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60062</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice Presidnet - Controller</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>COMMON STOCK</value>
            </securityTitle>
            <transactionDate>
                <value>2004-10-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2250</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>35.5</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>115837</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">ON MAY 28, 2004, THE COMMON STOCK OF IDEX WAS SPLIT 3 FOR 2 RESULTING IN THE REPORTING PERSON'S ACQUISITION OF 39,362 ADDITIONAL SHARES OF COMMON STOCK.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>CLINTON L. KOOMAN</signatureName>
        <signatureDate>2004-10-27</signatureDate>
    </ownerSignature>
</ownershipDocument>

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