A projection exposure apparatus comprises a wafer stage for supporting a wafer thereon and two-dimensionally moving the wafer along an image plane substantially perpendicular to an optical axis of a projection optical system, first position detecting means for measuring a two-dimensional position of the wafer stage to detect its coordinates with respect to the optical axis of the wafer, a reticle stage for holding different original patterns such that the patterns do not overlap each other and that predetermined central exposure points of the original image patterns are located at predetermined intervals, and for two-dimensionally moving the reticles at a stroke given such that the optical axis of projection passes all central exposure points of the different original patterns, and second position detecting means for detecting a two-dimensional position of the reticle stage according to a coordinate system determined by the first detecting means and a coordinate system having its axes along the same directions as those of the coordinate system determined by the first detecting means.