A display optical system for guiding light from an image to an observer or a surface projecting an image thereon with a first optical system and second optical system. The first optical system having a first surface formed on a transparent body with a reflecting action, a second surface reflecting light reflected on the first surface toward the first surface again, and a third surface formed on the transparent body transmitting light from the image. The light transmitted through the third surface travels toward the first surface and is reflected for the first time. In addition, a principal ray, central angle of view to be reflected for the last time on the first surfaces is reflected to a side opposite a side of the first reflection on the first surface with respect to a normal line of a surface on a hit point thereof.