PURPOSE: To illuminate region to be illuminated with high luminous efficiency and illuminance without making the electric power of a light source larger even if a narrow illuminated region and a small illuminating numerical aperture are given as the specification.

CONSTITUTION: Light from a mercury lamp 1 is reflected/converged by the rotary ellipsoid of a converging mirror 2 and the image of the real image of the light emitting part of the mercury lamp 1 is formed on an image forming point 22A with the light converged by a correcting optical system 9. The light from the real image is converted into a roughly parallel luminous flux by a collimater lens 3 and supplied to a fly eye lens 5 and the illuminated region 8 is illuminated with the light from a large number of source images on the light exit surface of the fly eye lens 5 via a condenser lens 7.