To detect the relative positional relationship between a reticle and a wafer at high speed with high accuracy by projecting alignment patterns on alignment marks successively, and detecting the relative positions of the reticle and the wafer from a changing pattern of a quantity of charged particles generated from the alignment marks when projecting the patterns on the marks.

Alignment patterns for one-time exposure are disposed at equal intervals and alignment marks for one-time exposure are disposed also at equal intervals. The intervals between the images of the alignment patterns are a little bit different from the intervals between the alignment marks. This is one type of applications of verniers. By this method, the relative positional relationship between a reticle and a wafer can be calculated by an easy method such as calculating the position of the center of gravity and finding out a point of intersection between the lines which connect the center of each bar of a bar graph, without relying on a complicated pattern matching.