An input waveguide (6) having one end connected between an L-shaped waveguide (1a) and an L-shaped waveguide (1f) and another end connected to the PORT (1); an output waveguide (7) having one end connected between the L-shaped waveguide (1a) and a flat waveguide (1b) and another end connected to the PORT (2); an output waveguide (8) having one end connected between the flat waveguide (1b) and an L-shaped waveguide (1c) and another end connected to the PORT (3); an output waveguide (9) having one end connected between the L-shaped waveguide (1c) and an L-shaped waveguide (1d) and another end connected to the PORT (4); and a plurality of branching waveguides (10) each having one end connected to the output waveguide (7) and another end connected to the output waveguide (8) are provided.