An illumination apparatus is disclosed, with which an illumination optical system can be made small while attaining uniform light distribution properties within an irradiation region of light, by properly designing the shape of a reflection member. The illumination apparatus of the present invention includes a light source and a reflection member which reflects toward an irradiated side a first light flux emerging from the light source and having an emergence angle with respect to an irradiation optical axis which is larger than a predetermined angle. The reflection member reflects a light ray of the first light flux for which the emergence angle is maximal in a direction intersecting with the irradiation optical axis, and satisfies the following condition: .theta.1<.theta.2 where .theta.1 and .theta.2 are angles defined by, respectively, a first and a second light ray before and after reflection at the reflection surface.