A terminal block includes a housing including a connection surface to which an electromagnetic relay is connectable. The housing includes at least one attachment groove that opens to the connection surface and extends toward inside of the housing. The at least one attachment groove includes a first groove portion ami a second groove portion are disposed adjacent to and communicating with each other. The first groove portion includes a first narrow width portion disposed near the connection surface, a wide width portion disposed farther from the connection surface than the first narrow width portion, and a step portion at a boundary of the first narrow width portion and the wide width portion, the step portion being capable of restricting a movement of the holding member in a removal direction. The second groove portion is configured to be capable of accommodating the claw portion without elastically deforming.