To always ensure a high-accuracy exposure, without influence of partial irregularity of exposing regions on a photosensitive substrate surface.

Before exposure, a wafer W is moved in a two-dimensional plane, the positions at measuring points e.g. P4-P6 on the optical axis (Z) of the wafer surface are measured to see the irregularity, and the best imaging plane Fo of a projection optical system is measured. Face elements 62 of a wafer holder 25 for vacuum chucking the back side of the wafer W are driven by specified lengths along the optical axis to align the wafer surface with the best imaging plane Fo of the optical system, thus always ensuring a high- accuracy exposure.