A manufacturing method of a photomask by which a resist pattern corresponding to a pattern with designed values can be formed, a method for optical proximity correction, and a manufacturing method of a semiconductor device are provided. Proximity design features that are close to each other and estimated to violate a mask rule check are extracted. In the proximity design features, correction prohibited regions where optical proximity correction is not carried out are set based on the distance between the features obtained from the extracted proximity design features and the resolution of an exposure device. Optical proximity correction is carried out on the proximity design features with the correction prohibited regions excluded to obtain corrected proximity patterns. A predetermined mask material is patterned by carrying out electron beam lithography based on the corrected proximity pattern data.