PURPOSE: To etch efficiently and easily the pattern part of a mask layer with high accuracy by coating the mask layer on a mask substrate with a positive type resist layer, exposing a part of the resist layer on the peripheral part of the substrate when the resist layer is exposed through a prescribed mask pattern, and utilizing the exposed part for judging the end of etching.

CONSTITUTION: A chromium layer and a chromium oxide layer are successively vapor-deposited on a glass plate 1 to form a mask layer 21, and the layer 21 is coated with a positive type resist layer 31. The layer 31 is exposed through a prescribed mask pattern such as an IC pattern with a photo-repeater, and a part of the layer 31 on the peripheral part of the plate 1 is exposed through a prescribed pattern such as a rectangular pattern 6mm square by step and repeat exposure with the photo-repeater. Etching is then carried out. At this time, the etching of the mask pattern part of the layer 21 and the etching of the peripheral part 52 are simultaneously started, and they proceed at the same speed. It is difficult to judge whether the etching of the mask pattern part is finished or not by seeing, but the end of the etching of the part 52 can be easily recognized by seeing because of the large area.