To provide a light incident/exit part of an optical device that reduces the number of constituting optical elements and that realizes easy alignment or assembling operation, low cost, simplified manufacturing, etc.

The light incident/exit part of an optical device is constituted of a plurality of waveguides and a single lens, wherein the light incident/exit end face of each waveguide is formed oblique so that the exiting light from each waveguide is made incident on the lens, by transversely propagating the optical axis of the lens and that the optical axis of each propagating light exiting from the lens is made parallel to each other. In addition, the waveguides are constituted of optical fibers, with a ferrule provided holding the optical fibers, and with the ferrule holding all optical fibers, in such a manner that the center axes of all optical fibers are equidistant with respect to the lens optical axis. Also, the light incident/exit end face of all optical fibers is formed oblique at identical tilt angle.