<SEC-DOCUMENT>0001127602-13-016164.txt : 20130508
<SEC-HEADER>0001127602-13-016164.hdr.sgml : 20130508
<ACCEPTANCE-DATETIME>20130508172400
ACCESSION NUMBER:		0001127602-13-016164
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20130507
FILED AS OF DATE:		20130508
DATE AS OF CHANGE:		20130508

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Bietz Steven L
		CENTRAL INDEX KEY:			0001355208

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-03480
		FILM NUMBER:		13825654

	MAIL ADDRESS:	
		STREET 1:		P. O. BOX 5601
		CITY:			BISMARCK
		STATE:			ND
		ZIP:			58506-5601

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MDU RESOURCES GROUP INC
		CENTRAL INDEX KEY:			0000067716
		STANDARD INDUSTRIAL CLASSIFICATION:	MINING, QUARRYING OF NONMETALLIC MINERALS (NO FUELS) [1400]
		IRS NUMBER:				410423660
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1200 WEST CENTURY AVENUE
		CITY:			BISMARCK
		STATE:			ND
		ZIP:			58503
		BUSINESS PHONE:		701-530-1059

	MAIL ADDRESS:	
		STREET 1:		1200 WEST CENTURY AVENUE
		CITY:			BISMARCK
		STATE:			ND
		ZIP:			58503

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MONTANA DAKOTA UTILITIES CO
		DATE OF NAME CHANGE:	19850429
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-05-07</periodOfReport>

    <issuer>
        <issuerCik>0000067716</issuerCik>
        <issuerName>MDU RESOURCES GROUP INC</issuerName>
        <issuerTradingSymbol>MDU</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001355208</rptOwnerCik>
            <rptOwnerName>Bietz Steven L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>WBI ENERGY, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1250 WEST CENTURY AVENUE</rptOwnerStreet2>
            <rptOwnerCity>BISMARCK</rptOwnerCity>
            <rptOwnerState>ND</rptOwnerState>
            <rptOwnerZipCode>58503</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Pres. &amp; CEO - WBI Energy, Inc.</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-05-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>26.3733</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>23884.592</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock - (401-k)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>35345.995</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trustee</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock - (ESOP)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>292.164</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trustee</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The price reported in column 4 is the weighted average sale price.  The shares were sold in multiple transactions at prices ranging from $26.310 to $26.445, inclusive.  The reporting person undertakes to provide to MDU Resources Group, Inc., any shareholder of MDU Resources Group, Inc. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price.</footnote>
        <footnote id="F2">As of the most recent quarter end.  The number of shares may fluctuate daily depending on plan activity in the fund.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Steven L. Bietz</signatureName>
        <signatureDate>2013-05-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
