Resist film patterns are formed on a light shielding film formed on a surface of the glass substrate. The resist film patterns cover regions A and B of the surface of the substrate. Then, using the resist film patterns as a mask, the light shielding film is patterned to form the light shielding film pattern in the regions A and B. The light shielding film pattern formed in region B is used as a dummy pattern. Then, a further resist film is formed over the light shielding film patterns of the regions A and B. The resist film is patterned to provide only a resist film pattern covering the region A. Thereafter, an etching processing is applied for removing the light shielding film pattern in the region B using the resist film pattern as a mask. In this method, the presence of the dummy pattern is an important feature.