A surface (17d′) facing a photoelectric conversion apparatus is formed on the optical block (3) side, said surface having light from a light emitting element (10) inputted thereto and monitor light outputted therefrom, and a coupling light output surface (12) having coupling light outputted therefrom is formed on the optical housing (4) side, and consequently, the surface (17d′) and the coupling light output surface (12) are simply and highly accurately formed. Then, an optical block (3) and an optical housing (4) are simply and accurately combined by being fitted together by means of fitting sections (21, 24). Adhesion of foreign materials and formation of scratches on the reflecting surface (18) of the optical block (3) are suppressed by covering the reflecting surface (18) with the optical housing (4).