-----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,
 ITmm6mxfMKNPlSeXq7UAvQjtG+hogOEBzTsyjQde++G3Om9DRLegrk/s4Wk/e0PD
 xjcVM2e9v4plbTghslVp7w==

<SEC-DOCUMENT>0000082811-04-000026.txt : 20040423
<SEC-HEADER>0000082811-04-000026.hdr.sgml : 20040423
<ACCEPTANCE-DATETIME>20040423174447
ACCESSION NUMBER:		0000082811-04-000026
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040422
FILED AS OF DATE:		20040423

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

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			GRAFF STEPHEN N
		CENTRAL INDEX KEY:			0001210933

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-07283
		FILM NUMBER:		04752169

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

	MAIL ADDRESS:	
		STREET 1:		805 LONG TREE ROAD
		CITY:			ELM GROVE
		STATE:			WI
		ZIP:			53122
</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>0001210933</rptOwnerCik>
            <rptOwnerName>GRAFF STEPHEN N</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>805 LONG TREE ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ELM GROVE</rptOwnerCity>
            <rptOwnerState>WI</rptOwnerState>
            <rptOwnerZipCode>53122</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 options</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>2014-04-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Non-qualified stock option</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>37000</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 (4000) shares become exercisable on the date of the Corporation's Annual Shareholders Meeting in each of the next four years as long as the Director remains in office.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Stephen N. Graff by Kenneth F. Kaplan POA</signatureName>
        <signatureDate>2004-04-23</signatureDate>
    </ownerSignature>
</ownershipDocument>

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