A non-reciprocal circuit device includes a lower metal case, a terminal resin case, a central-electrode assembly, an upper metal case, and a permanent magnet. The central-electrode assembly includes a ferrite to which a dc magnetic field is applied by the permanent magnet, and central electrodes disposed around the ferrite. The terminal resin case includes two sets of opposing side walls and a bottom wall, and cut surfaces formed when a lead frame is separated are provided in one set of side walls, respectively. Terminals for surface mounting are provided on another set of side walls which is different from the one set of side walls.