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

    <schemaVersion>X0202</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2007-05-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0000351346</issuerCik>
        <issuerName>BIOMET INC</issuerName>
        <issuerTradingSymbol>BMET</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001331721</rptOwnerCik>
            <rptOwnerName>Schiess Steven F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>4555 RIVERSIDE DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PALM BEACH GARDENS</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33410</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Vice President</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-05-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>96</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>42.09</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3886</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>401(k) Savings/Retirement Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These shares represent the Company's contribution to the Reporting Person's Account in what was formerly the Company's Employee Stock Bonus Plan.  (Effective 4-1-2007, the Reporting Person may elect to participate in the Biomet 401(k) Savings and retirement Plan which combines two previous plans:  Biomet's 401(k) Profit Sharing Plan and Trust and Biomet's Employee Stock Bonus Plan.)  These shares were acquired in routine exempt acquisitions pursuant to Rule 16b-3 on a periodic basis between June 1, 2006 and May 31, 2007.  The information reported herein is based upon estimate provided by the Plans' recordkeeper as of May 31, 2007.</footnote>
        <footnote id="F2">This represents the average price of shares acquired in the reporting person's account during the time period June 1, 2006 and May 31, 2007 through the Biomet, Inc. Employee Stock Bonus Plan qualified under Section 401(a) of the Internal Revenue Code, which was merged into the Biomet 401(k) Savings and Retirement Plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Jacqueline K. Huber POA for Steven Schiess</signatureName>
        <signatureDate>2007-07-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
