Abstract: A breaker includes a fixed metal plate, a moving metal plate, a bimetal, and a heater. The fixed plate includes a fixed contact in a space of an exterior case having an electrically-insulating case and an exterior metal plate. The exterior plate and the fixed plate are arranged opposed to each other, and fixed to the electrically-insulating case. The bimetal has a convex shape, and is arranged between the heater and the moving plate. The electrically-insulating case includes first and second outer walls and protruding from the both ends of the case. A central part of the fixed plate is fixed to the first outer wall, and a part of moving plate is fixed to the second outer wall. The exterior plate closes the opening of the space.