Optical waveguides and optical transmission/reception units are placed on one principal plane of a semiconductor substrate. A light source is placed on one end surface of the semiconductor substrate and guides generated light to the optical waveguides. In the optical transmission/reception units, each of optical resonant members optically resonates with partial light of one of light beams propagating in the optical waveguides and emits the partial light into an optical transmission member if voltage is applied thereto. In the optical transmission/reception units, each of another optical resonant members optically resonates with light propagating in the optical transmission member and emits the resonated light into a photodetector unit if voltage is applied thereto.