In order to achieve a phase shift circuit whereby excellent reflection characteristics and a desired phase shift quantity at a center frequency can be obtained without increasing the length in the traveling direction, the present invention is provided with: an input waveguide having an input terminal at one end; an output waveguide having an output terminal at one end; a center waveguide, which has a thickness that is smaller than that of the input waveguide or that of the output waveguide, and which has a different center position in the thickness direction with respect to the input waveguide or the output waveguide; a first tapered waveguide connecting to each other the other end of the input waveguide and one end of the center waveguide; and a second tapered waveguide connecting to each other the other end of the output waveguide and the other end of the center waveguide.
