A three-way power divider , comprising: a rectangular waveguide having a waveguide wall, the waveguide wall being formed by a first L-shaped waveguide , a first flat waveguide , a second L-shaped waveguide , a third L-shaped waveguide , a second flat waveguide (le), and a fourth L-shaped waveguide arranged in a ring shape; an input waveguide having one end connected between the first L-shaped waveguide (la) and the fourth L-shaped waveguide and another end connected to a first port ; a first output waveguide having one end connected between the first L-shaped waveguide (la) and the first flat waveguide and another end connected to a second port ; a second output waveguide having one end connected between the first flat waveguide and the second L-shaped waveguide and another end connected to a third port ; a third output waveguide having one end connected between the second L-shaped waveguide and the third L-shaped waveguide , or between the second flat waveguide and the fourth L-shaped waveguide and another end connected to a fourth port ; and a plurality of branching waveguides each having one end connected to the first output waveguide and another end connected to the second output waveguide ., wherein a difference between a sum of electrical lengths of the second L-shaped waveguide , the third L-shaped waveguide , the second flat waveguide (le), and the fourth L-shaped waveguide and a sum of electrical lengths of the first L-shaped waveguide (la) and the first flat waveguide is a multiple of a half of a wavelength of a propagating signal by a factor of N, N being an odd number, at a frequency of a fundamental wave of the propagating signal. a rectangular waveguide having a waveguide wall, the waveguide wall being formed by a first L-shaped waveguide , a first flat waveguide , a second L-shaped waveguide , a third L-shaped waveguide , a second flat waveguide (le), and a fourth L-shaped waveguide arranged in a ring shape; an input waveguide having one end connected between the first L-shaped waveguide (la) and the fourth L-shaped waveguide and another end connected to a first port ; a first output waveguide having one end connected between the first L-shaped waveguide (la) and the first flat waveguide and another end connected to a second port ; a second output waveguide having one end connected between the first flat waveguide and the second L-shaped waveguide and another end connected to a third port ; a third output waveguide having one end connected between the second L-shaped waveguide and the third L-shaped waveguide , or between the second flat waveguide and the fourth L-shaped waveguide and another end connected to a fourth port ; and a plurality of branching waveguides each having one end connected to the first output waveguide and another end connected to the second output waveguide ., wherein a difference between a sum of electrical lengths of the second L-shaped waveguide , the third L-shaped waveguide , the second flat waveguide (le), and the fourth L-shaped waveguide and a sum of electrical lengths of the first L-shaped waveguide (la) and the first flat waveguide is a multiple of a half of a wavelength of a propagating signal by a factor of N, N being an odd number, at a frequency of a fundamental wave of the propagating signal. <EOS>