A housing (12) of a board connector (10) to be connected to a circuit board (P) is disposed such that a connection surface to a mating connector (50) is exposed to outside through an opening (41) of a case (40) capable of accommodating the circuit board (P) inside. The housing (12) includes outer locking protrusions (31) for locking a peripheral edge part of the opening (41) of the case (40) from outside of the case (40) so that the board connector (10) will not displace into the case (40) due to forces exerted by a mating connector (50) during a connection operation.