To enable the formation highly accurate and fine resist patterns by regularly forming the desired patterns of a mask for forming the fine patterns and the dummy patterns.

A photoresist is subjected to the first exposure by using a first photomask 11 and this photoresist is subjected to the second exposure by using a second photomask 12. The required resist patterns are formed on the photoresist by the first exposure and the second exposure. In such a case, the first photomask 11 is formed with the desired patterns 101 and the dummy patterns 102 at respective regularly arranged plural grid points. The second photomask 12 is formed with the dummy patterns 102 of the size larger than the size of the first patterns at the selected grid points among the plural grid points described above. Even if the patterns are formed finer, the regular arrangement of the desired patterns and the dummy patterns is possible. The repeating characteristic of the patterns is assured by the exposure using the first photomask 11, by which DOF is improved and the exposure of the highly accurate and fine patterns and the formation of the resist patterns are made possible.