-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 WyWXye2VGvfp9io+Vsm8TDpT/a/S7h/P1hgAFyMk738NTiKYcdwC9DbEOiVjMWQ9
 ++L+K2K100GS6VxIuCgfLg==

<SEC-DOCUMENT>0000082811-04-000024.txt : 20040423
<SEC-HEADER>0000082811-04-000024.hdr.sgml : 20040423
<ACCEPTANCE-DATETIME>20040423171122
ACCESSION NUMBER:		0000082811-04-000024
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040422
FILED AS OF DATE:		20040423

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			DOERR CHRISTOPHER L
		CENTRAL INDEX KEY:			0001183642

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-07283
		FILM NUMBER:		04751857

	BUSINESS ADDRESS:	
		STREET 1:		C/O APOGENT TECHNOLOGIES
		STREET 2:		30 PENHALLOW STREET
		CITY:			PORTSMOUTH
		STATE:			NH
		ZIP:			03801
		BUSINESS PHONE:		6034336131

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			REGAL BELOIT CORP
		CENTRAL INDEX KEY:			0000082811
		STANDARD INDUSTRIAL CLASSIFICATION:	MOTORS & GENERATORS [3621]
		IRS NUMBER:				390875718
		STATE OF INCORPORATION:			WI
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		200 STATE ST
		CITY:			BELOIT
		STATE:			WI
		ZIP:			53511
		BUSINESS PHONE:		6083648800

	MAIL ADDRESS:	
		STREET 1:		200 STATE STREET
		CITY:			BELOIT
		STATE:			WI
		ZIP:			53511-6254

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	BELOIT TOOL CORP
		DATE OF NAME CHANGE:	19730522

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	RECORD A PUNCH CORP
		DATE OF NAME CHANGE:	19690320
</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>2004-04-22</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000082811</issuerCik>
        <issuerName>REGAL BELOIT CORP</issuerName>
        <issuerTradingSymbol>RBC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001183642</rptOwnerCik>
            <rptOwnerName>DOERR CHRISTOPHER L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>900 CHEYENNE AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 100</rptOwnerStreet2>
            <rptOwnerCity>GRAFTON</rptOwnerCity>
            <rptOwnerState>WI</rptOwnerState>
            <rptOwnerZipCode>53024</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-qualified stock option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>20.3</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-04-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>20.3</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2004-04-22</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-04-22</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Non-qualified stock option</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>23000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Four thousand (4000) shares are immediately exercisable and four thousand (4,000) become exercisable on date of the Corporation's Annual Shareholders Meeting in each of the next four years as long as the non-employee director remains in office.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Christopher L. Doerr by Kenneth F. Kaplan POA</signatureName>
        <signatureDate>2004-04-23</signatureDate>
    </ownerSignature>
</ownershipDocument>

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