A connector comprises a first member and a second member. The first member has a lock spring portion, a lock portion and a regulated portion. When the connector and a mating connector are in a mated state where the connector and the mating connector are mated with each other, the lock portion locks the mated state together with a locked portion of the mating connector. The first member is configured so that, when the mating connector is forced to be unmated from the connector under the mated state, the lock spring portion is resiliently deformed so that each of the lock portion and the regulated portion is moved in a combined direction of upward in an up-down direction and a first horizontal direction. The second member has a deformation-preventing portion provided with a regulating portion. A range of the movement of the regulated portion is defined by the regulating portion.