-----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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 IDFs7FJ4e0rneZIeqUI8Fg==

<SEC-DOCUMENT>0000908662-09-000375.txt : 20091217
<SEC-HEADER>0000908662-09-000375.hdr.sgml : 20091217
<ACCEPTANCE-DATETIME>20091217150118
ACCESSION NUMBER:		0000908662-09-000375
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20091215
FILED AS OF DATE:		20091217
DATE AS OF CHANGE:		20091217

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			LATOUR RICHARD F
		CENTRAL INDEX KEY:			0001243500

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-14771
		FILM NUMBER:		091247047

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MICROFINANCIAL INC
		CENTRAL INDEX KEY:			0000827230
		STANDARD INDUSTRIAL CLASSIFICATION:	MISCELLANEOUS BUSINESS CREDIT INSTITUTION [6159]
		IRS NUMBER:				042962824
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		10 M COMMERCE WAY
		CITY:			WOBURN
		STATE:			MA
		ZIP:			01801
		BUSINESS PHONE:		7819944800

	MAIL ADDRESS:	
		STREET 1:		10 M COMMERCE WAY
		CITY:			WOBURN
		STATE:			MA
		ZIP:			01801

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	BOYLE LEASING TECHNOLOGIES INC
		DATE OF NAME CHANGE:	19980605
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-12-15</periodOfReport>

    <issuer>
        <issuerCik>0000827230</issuerCik>
        <issuerName>MICROFINANCIAL INC</issuerName>
        <issuerTradingSymbol>MFI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001243500</rptOwnerCik>
            <rptOwnerName>LATOUR RICHARD F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10-M COMMERCE WAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WOBURN</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01801</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Pres/CEO/Treasurer/Clerk/Sec</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2009-12-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>200</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.95</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>490807</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2009-12-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>456</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.95</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>491263</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Eugene W. McDermott as attorney-in-fact</signatureName>
        <signatureDate>2009-12-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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