An optical device unit including optical fibers for input and output, a lens and a reflective/semitransparent optical element, wherein, to enable optical design with a degree of freedom, lenses the number of which is the same as the optical fibers for input and output are provided and the optical fibers, the lenses and the reflective/semitransparent optical element are disposed so that the input/output end of each optical fiber, the optical axis center of the lens and reflection/transmission point on the reflective/semitransparent optical element are aligned.