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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2007-12-17</periodOfReport>

    <dateOfOriginalSubmission>2007-12-18</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001332341</issuerCik>
        <issuerName>US BioEnergy CORP</issuerName>
        <issuerTradingSymbol>USBE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001214050</rptOwnerCik>
            <rptOwnerName>ATKINSON RICHARD K</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>PO BOX 30150</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>RENO CITY</rptOwnerCity>
            <rptOwnerState>NV</rptOwnerState>
            <rptOwnerZipCode>89520</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Senior VP and CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-12-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>393</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.14</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>52634</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This amendment is being filed, in part, to correct an error in the price of the securities delivered incident to the vesting of securities issued in accordance with Rule 16b-3. The Form 4 filed on 12/18/07 inadvertently listed the price as $0.</footnote>
        <footnote id="F2">This amendment is being filed, in part, to correct an error in the number of securities previously reported to be beneficially owned by the reporting person. The Form 4 filed 12/18/07 inadvertently understated by 1,238 shares the number of shares of common stock of US BioEnergy Corporation beneficially owned by the reporting person.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Gregory S. Schlicht, by power of attorney</signatureName>
        <signatureDate>2008-03-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
