An optical phase diversity receiver may include: a diffraction grating including grating surfaces; a first input waveguide to which a first optical signal is inputted; a second input waveguide to which a second optical signal is inputted; and a slab waveguide including an input terminal optically coupled with the first and second input waveguides, and an output terminal provided at a position at which optical signals reflected by the diffraction grating reach the slab waveguide. Every determined number of grating surfaces are chirped in an identical manner. The slab waveguide is configured to guide the first and the second optical signals to the diffraction grating and guide the optical signals reflected by the diffraction grating to the output terminal. The grating surfaces are configured such that each of the optical signals reflected by the diffraction grating is divided into the predetermined number by optical power distribution.