An optical semiconductor module comprises an optical transmission channel including a waveguide transmitting a light beam, a holding member whose holding member holds the channel with the end of the channel being exposed from the surface, electric wiring formed on the surface, an optical semiconductor element, mounted above the surface, including an active area to emit or receive a light beam and an electrode pad electrically connected to the electric wiring, the active area optically coupled to the waveguide at the end of the channel, and an electrical insulation film between the optical semiconductor element and the holding member, including openings each corresponding to an electrical connection between the electrode pad and the electric wiring, and an optically coupling portion between the active area and the waveguide, the electrical insulation film being in contact with a portion of the end of the channel.