To obtain a transmission and reception integrated optical system unit with less number of components, less number of manufacturing man-hours and a small connection loss.

A V-shaped V groove 10 is formed to one side face of a Si substrate 4, a light emitting element 6 is mounted on the side face, another V-groove 10 is formed on the other side face and a light receiving element 7 is mounted onto the other side face. Furthermore, a transmission optical fiber connected to the light emitting element 6 and a light receiving optical fiber 3 connected to the light receiving element are molded integrally and end faces at the tip of the molded side of the transmission optical fiber 2 and the light receiving optical fiber 3 are used for transmission reception ends to configure an optical connector. Let a thickness of the substrate 4 be a thickness where the interval between both the transmission reception fibers is equal to an interval of the fibers of the optical connector, then a polymer optical guide path for adjusting the fiber interval is not required. Thus, the unit is configured as an integrated type without any joint while not exerting any stress onto the optical fibers.