<?xml version="1.0"?>
<edgarSubmission>

    <schemaVersion>X0704</schemaVersion>

    <submissionType>D/A</submissionType>

    <testOrLive>LIVE</testOrLive>

    <primaryIssuer>
        <cik>0001370913</cik>
        <entityName>MAGNUM SEMICONDUCTOR INC</entityName>
        <issuerAddress>
            <street1>591 YOSEMITE DR</street1>
            <city>MILPITAS</city>
            <stateOrCountry>CA</stateOrCountry>
            <stateOrCountryDescription>CALIFORNIA</stateOrCountryDescription>
            <zipCode>98538</zipCode>
        </issuerAddress>
        <issuerPhoneNumber>408-934-3700</issuerPhoneNumber>
        <jurisdictionOfInc>DELAWARE</jurisdictionOfInc>
        <issuerPreviousNameList>
            <value>None</value>
        </issuerPreviousNameList>
        <edgarPreviousNameList>
            <value>None</value>
        </edgarPreviousNameList>
        <entityType>Corporation</entityType>
        <yearOfInc>
            <overFiveYears>true</overFiveYears>
        </yearOfInc>
    </primaryIssuer>

    <relatedPersonsList>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Gopal</firstName>
                <lastName>Solanki</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>591 Yosemite Drive</street1>
                <city>Milpitas</city>
                <stateOrCountry>CA</stateOrCountry>
                <stateOrCountryDescription>CALIFORNIA</stateOrCountryDescription>
                <zipCode>95035</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Andy</firstName>
                <lastName>Rappaport</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>591 Yosemite Drive</street1>
                <city>Milpitas</city>
                <stateOrCountry>CA</stateOrCountry>
                <stateOrCountryDescription>CALIFORNIA</stateOrCountryDescription>
                <zipCode>95035</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Jack</firstName>
                <lastName>Guedj</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>591 Yosemite Drive</street1>
                <city>Milpitas</city>
                <stateOrCountry>CA</stateOrCountry>
                <stateOrCountryDescription>CALIFORNIA</stateOrCountryDescription>
                <zipCode>95035</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Jose</firstName>
                <lastName>Suarez</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>591 Yosemite Drive</street1>
                <city>Milpitas</city>
                <stateOrCountry>CA</stateOrCountry>
                <stateOrCountryDescription>CALIFORNIA</stateOrCountryDescription>
                <zipCode>95035</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Andrew</firstName>
                <lastName>Flett</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>591 Yosemite Drive</street1>
                <city>Milpitas</city>
                <stateOrCountry>CA</stateOrCountry>
                <stateOrCountryDescription>CALIFORNIA</stateOrCountryDescription>
                <zipCode>95035</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Terence</firstName>
                <lastName>Griffin</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>591 Yosemite Drive</street1>
                <city>Milpitas</city>
                <stateOrCountry>CA</stateOrCountry>
                <stateOrCountryDescription>CALIFORNIA</stateOrCountryDescription>
                <zipCode>95035</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
    </relatedPersonsList>

    <offeringData>
        <industryGroup>
            <industryGroupType>Other Technology</industryGroupType>
        </industryGroup>
        <issuerSize>
            <revenueRange>Decline to Disclose</revenueRange>
        </issuerSize>
        <federalExemptionsExclusions>
            <item>06</item>
        </federalExemptionsExclusions>
        <typeOfFiling>
            <newOrAmendment>
                <isAmendment>true</isAmendment>
                <previousAccessionNumber>0001370913-10-000003</previousAccessionNumber>
            </newOrAmendment>
            <dateOfFirstSale>
                <value>2010-04-08</value>
            </dateOfFirstSale>
        </typeOfFiling>
        <durationOfOffering>
            <moreThanOneYear>false</moreThanOneYear>
        </durationOfOffering>
        <typesOfSecuritiesOffered>
            <isEquityType>true</isEquityType>
        </typesOfSecuritiesOffered>
        <businessCombinationTransaction>
            <isBusinessCombinationTransaction>false</isBusinessCombinationTransaction>
            <clarificationOfResponse></clarificationOfResponse>
        </businessCombinationTransaction>
        <minimumInvestmentAccepted>0</minimumInvestmentAccepted>
        <salesCompensationList></salesCompensationList>
        <offeringSalesAmounts>
            <totalOfferingAmount>20000000</totalOfferingAmount>
            <totalAmountSold>11459635</totalAmountSold>
            <totalRemaining>8540365</totalRemaining>
            <clarificationOfResponse></clarificationOfResponse>
        </offeringSalesAmounts>
        <investors>
            <hasNonAccreditedInvestors>false</hasNonAccreditedInvestors>
            <totalNumberAlreadyInvested>26</totalNumberAlreadyInvested>
        </investors>
        <salesCommissionsFindersFees>
            <salesCommissions>
                <dollarAmount>0</dollarAmount>
            </salesCommissions>
            <findersFees>
                <dollarAmount>0</dollarAmount>
            </findersFees>
            <clarificationOfResponse></clarificationOfResponse>
        </salesCommissionsFindersFees>
        <useOfProceeds>
            <grossProceedsUsed>
                <dollarAmount>0</dollarAmount>
            </grossProceedsUsed>
            <clarificationOfResponse></clarificationOfResponse>
        </useOfProceeds>
        <signatureBlock>
            <authorizedRepresentative>false</authorizedRepresentative>
            <signature>
                <issuerName>MAGNUM SEMICONDUCTOR INC</issuerName>
                <signatureName>/s/ Terence Griffin</signatureName>
                <nameOfSigner>Terence Griffin</nameOfSigner>
                <signatureTitle>Chief Financial Officer</signatureTitle>
                <signatureDate>2010-05-21</signatureDate>
            </signature>
        </signatureBlock>
    </offeringData>
</edgarSubmission>
