A connector with a lock mechanism has a connector main body in which are mounted electric contacts, a shield member for covering the connector main body and a connecting portion between the electric contacts and a cable, a casing for enclosing the connector main body and the shield member; and a lock mechanism for locking or unlocking a connection of the connector to a mating connector. The lock mechanism is made up of a flexible lock piece one end of which is connected to the shield member; a pair of lock release slide plates which are slidable along upper and lower main surfaces of the casing; and slide members which slide inside the casing by sliding of the slide plates so as to release the locking by the lock piece.