<SEC-DOCUMENT>0001209191-21-030821.txt : 20210507
<SEC-HEADER>0001209191-21-030821.hdr.sgml : 20210507
<ACCEPTANCE-DATETIME>20210507142941
ACCESSION NUMBER:		0001209191-21-030821
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210505
FILED AS OF DATE:		20210507
DATE AS OF CHANGE:		20210507

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Moore Charles O
		CENTRAL INDEX KEY:			0001543854

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36613
		FILM NUMBER:		21901916

	MAIL ADDRESS:	
		STREET 1:		110 RIVERBEND AVE
		CITY:			LEWIS CENTER
		STATE:			OH
		ZIP:			43035

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MIDDLEFIELD BANC CORP
		CENTRAL INDEX KEY:			0000836147
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				341585111
		STATE OF INCORPORATION:			OH

	BUSINESS ADDRESS:	
		STREET 1:		15985 E HIGH ST
		STREET 2:		P O BOX 35
		CITY:			MIDDLEFILED
		STATE:			OH
		ZIP:			44062-9263
		BUSINESS PHONE:		4406321666

	MAIL ADDRESS:	
		STREET 1:		15985 EAST HIGH STREET
		STREET 2:		P O BOX 35
		CITY:			MIDDLEFIELD
		STATE:			OH
		ZIP:			44062-9263
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-05-05</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000836147</issuerCik>
        <issuerName>MIDDLEFIELD BANC CORP</issuerName>
        <issuerTradingSymbol>MBCN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001543854</rptOwnerCik>
            <rptOwnerName>Moore Charles O</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>15985 EAST HIGH STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MIDDLEFIELD</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>44062</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President, Central Ohio Region</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-05-05</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>22.901</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4318.211</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Price reported in Column 4 is a weighted average price based on various purchase prices within a range.  For the 1,000 shares, the per share purchase prices ranged from $22.800 to $22.956.  The reporting person will, upon request, provide to MBCN, any security holder of MBCN, and the staff of the Securities and Exchange Commission full information regarding the number of shares purchased in each separate price within the range set forth in this footnote to this Form 4.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Charles O. Moore
by James R. Heslop, II
Power of Attorney</signatureName>
        <signatureDate>2021-05-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
