PURPOSE: To perform exposure of high precision, by finding a contrast amount of image formation between a mask mark and wafer one, to determine its maximum value and make a gap between the two become a given value so that high precision-gap setting can be performed.

CONSTITUTION: An alignment regulation device (comprising piezo-electric elements 4 and a stage 5) moves a and turns one or both of a mask 1 placed on a base, and a wafer 2 arranged facing the mask 1 and held on a check 3. A detection optical system (comprising object lenses 6, a light guide 10, half mirrors 8 and 9, and target marks 11) performs image formation of marks or patterns displayed on the mask 1 and the wafer 2, doing photoelectrical conversion of them. An operational control device (comprising a linear image senser-driving circuit 12, an interface circuit 13, and a computer 14) computes a contrast amount of image formation in a detection optical system and controls the alignment regulation device in accordance with the contrast amount. Thus exposure of high precision is performed.