An optical circuit, wherein the effects of reflected light generated by an optical component are reduced. The optical circuit (100) is provided with an optical branching (110) for branching light, an optical coupler (114) for coupling a first portion of branched light to an optical waveguide (118) for transmission, and an optical reflecting unit (116) for reflecting a second portion of the branched light, the phase difference between the reflected light from the optical coupler (114) and the reflected light from the optical reflecting unit (116) being (2m−1)π (where m is an integer) on an input side of the optical branching (110).