To obtain a display device which displays such high-quality pictures that do not cause a viewer to feel visually tired even when the viewer watches the pictures for a long time by realizing strict diopter adjustment.

This display device is constituted in such a way that the attaching surface 8a of a prism 1 having a freely curved surface is positioned in a plane perpendicular to the focal surface of the prism 1 and the side face of the attaching flange 7a of the prism 1 is put on the side faces of prism positioning steps of the prism attaching flange 7a of a holder 2. Therefore, a liquid crystal panel 4 can be prevented from contaminated with or scratched by dust and precise diopter setting can be performed continuously, because the prism 1 can be positioned and fixed with screws while the diopter is measured with a diopter measuring instrument, such as the dioptric tester, etc.