-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0000897077-05-000004.txt : 20050314
<SEC-HEADER>0000897077-05-000004.hdr.sgml : 20050314
<ACCEPTANCE-DATETIME>20050314114944
ACCESSION NUMBER:		0000897077-05-000004
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050314
FILED AS OF DATE:		20050314
DATE AS OF CHANGE:		20050314

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ALAMO GROUP INC
		CENTRAL INDEX KEY:			0000897077
		STANDARD INDUSTRIAL CLASSIFICATION:	FARM MACHINERY & EQUIPMENT [3523]
		IRS NUMBER:				741621248
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1502 E WALNUT
		CITY:			SEGUIN
		STATE:			TX
		ZIP:			78155
		BUSINESS PHONE:		8303791480

	MAIL ADDRESS:	
		STREET 1:		P.O. BOX 549
		STREET 2:		1502 EAST WALNUT
		CITY:			SEGUIN
		STATE:			TX
		ZIP:			78155

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			DAVIES GEOFF
		CENTRAL INDEX KEY:			0001120803

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-13854
		FILM NUMBER:		05677553

	BUSINESS ADDRESS:	
		STREET 1:		1502 EAST WALNUT
		CITY:			SEGUIN
		STATE:			TX
		ZIP:			78155

	MAIL ADDRESS:	
		STREET 1:		1502 EAST WALNUT
		CITY:			SEGIN
		STATE:			TX
		ZIP:			78155
</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>2005-03-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000897077</issuerCik>
        <issuerName>ALAMO GROUP INC</issuerName>
        <issuerTradingSymbol>ALG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001120803</rptOwnerCik>
            <rptOwnerName>DAVIES GEOFF</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1502 EAST WALNUT</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SEGIN</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>78155</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP of European Operations</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-03-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>100</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.38</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12100</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Derivative (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>14.38</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-03-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>100</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2003-02-13</value>
            </exerciseDate>
            <expirationDate>
                <value>2012-02-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1450</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Employee stock option granted pursuant to the Alamo Group Inc. 1994 Amended and Restated Incentive Stock Opton Plan.  Options becomes exercisable for up to 20% of total optioned shares after one year following grant date (2/13/02) and for an additional 20% in each succeeding year until fully exercisable at the end of the fifth year.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Geoffrey Davies</signatureName>
        <signatureDate>2005-03-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----