By using a forming die having a fixed die and a movable die moving along a parting surface on the fixed die and by moving the movable die along the parting surface, to press and hold a sintered part between the movable die and the fixed die, to form a cavity around the sintered part except parts which abut on the fixed die and the movable die by the forming die, and to fill the cavity with melted material which becomes an exterior part, so that the sintered part and the exterior part are integrated by insert molding.