A connector assembly is provided with a connector (first connector) to be mounted on a circuit board and a connector (second connector) for holding a flat cable flat wire member). When the two connectors are connected with each other, an end portion of the cable is inserted into the connector to bring conductors of the cable into contact with mating terminals. The connector is provided with a plate-shaped holder, and the cable is supported on this holder in such a state as to be displaceable in widthwise direction. On the other hand, the connector is provided with a pair of locking pieces as a positioning portion. When the two connectors are connected with each other, the respective locking pieces directly come into contact with the cable being inserted into the connector from widthwise outer sides, thereby positioning the cable with respect to the connector in widthwise direction. The respective conductors of the flat wire member can be more precisely and securely brought into contact with the mating terminals.