An apparatus for projection exposure which projects a pattern of a mask onto a work is provided. The apparatus has a base, a source of light, an optical system, a mask support mechanism, a work support mechanism and an alignment mechanism. The optical system constitutes light rays into projection light rays carrying image information of the mask, guiding the projection light rays through a predetermined optical path so that the projection light rays can be projected onto an exposure surface of the work. The optical system includes a projection optical system and an illumination optical system. The projection optical system is adapted to be disposed vertical relative to the base. The mask and work support mechanisms vertically support the mask and work relative to the base, respectively. In this way, the exposure surface of the work can coincide with an image forming plane in the optical path.