In a connector, a socket fitting portion of the socket housing and a header fitting portion of the header housing are fitted to each other to bring socket and header terminals and into contact with each other. In the socket housing, a socket terminal group including the plural socket terminals arranged in the longitudinal direction of the socket housing is provided only in a single line. In the header housing, a header terminal group including the plural header terminals arranged in the longitudinal direction of the header housing is provided only in a single line. It is, therefore, possible to minimize the connector in the width direction.