To provide an electrical connector for circuit boards having lock fittings designed to reliably prevent damage to lock portions and inadvertent removal of mating connectors. The lock fittings have lock plate portions that extend along the inner surface of the lateral walls of the housing and are retained in place on said lateral walls, or which extend along the inner surface of the end walls and are retained in place on said end walls; upright face-reinforcing plate portions that extend along the upright faces of the protruding wall of the housing facing said lock plate portions and are retained in place on said protruding wall; and connecting bottom portions that extend along the bottom wall and connect the bottom wall-adjacent end portions of the lock plate portions and the upright face-reinforcing plate portions.