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

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2006-07-05</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000913275</issuerCik>
        <issuerName>Solexa, Inc.</issuerName>
        <issuerTradingSymbol>SLXA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001368059</rptOwnerCik>
            <rptOwnerName>Lussier Richard H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SOLEXA, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>25861 INDUSTRIAL BLVD.</rptOwnerStreet2>
            <rptOwnerCity>HAYWARD</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94545</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP, Sales &amp; Field Operations</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>8.30</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2006-06-21</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2016-06-21</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>75000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Shares vest over four years from the date awarded with 25% vesting on the first anniversary of the date of grant, and the remainder vesting at a rate of 1/36 per complete month thereafter.  Shares are exercisable once vested.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Richard H Lussier</signatureName>
        <signatureDate>2006-07-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
