PURPOSE: To sharply shorten the measuring time of an optimum focal position by a method wherein patterns of the same shape are printed in several places of a resist on a wafer by changing their focal positions, contrasts of the individual patterns after their developing operation are computed and a regression analysis regarding the relationship between the contrasts and the focal positions is conducted.

CONSTITUTION: A wafer 26 is coated with a resist 25; patterns 21 of the same shape are printed in several places 23A to 23E by changing their focal positions. A developing operation is executed; after that, images of individual patterns 24A to 24E formed in said resist 25 are picked up; contrasts CA to CE of said individual patterns 24A to 24E are computed on the basis of image signals obtained by this image picking-up operation; in addition, a regression analysis regarding the relationship between the contrasts CA to CE and the focal positions is conducted. Thereby, an optimum focal position is measured. Thereby, since the optimum focal position can be measured by processing the image signals, it is not required to observe the wafer face visually by using a microscope. Consequently, the measuring time of the optimum focal position can shortened be sharply.