An image observing apparatus has two light sources, a scanning mirror upon which light beams from the two light sources are incident in common, and two optical systems. The two optical systems respectively lead the light beams emitted from the two light sources and scanned by the scanning mirror to the right and left eyes of an observer. The light beams emitted respectively from the two light sources are scanned by the scanning mirror and form two-dimensional images for the right and left eyes on predetermined surfaces. Central field angle principal rays emitted respectively from the two light sources and reflected by the scanning mirror, exist on the same plane. Then, an angle made by the scanning mirror and by a surface vertical to the central field angle principal rays emerging from the two optical systems, is set so as to fall within a predetermined range.