A half region of an end face of an optical fiber is cut at an angle of 45.degree. to form a reflecting surface. A light-emitting element is arranged so as to face the end face of the optical fiber. A photoreceptor element is arranged beside the optical fiber with the element facing the reflecting surface. Transmitting light that has been emitted from the light-emitting element enters the end face of the optical fiber and passes through this optical fiber. Further, received light, which has been passed through the optical fiber is reflected by the reflecting surface and emitted from the side of the optical fiber, and then it enters the photoreceptor element. This allows the transmitting light and the received light to be separated from each other without using any optical component.