A data generating method by which a computer accessible to a light pattern storage unit stored with a shape of a light exposure pattern formed on a substrate by a light exposure on the basis of design data of a semiconductor device and to an electron beam exposure pattern storage unit stored with a shape of an electron beam exposure pattern formed on the substrate by an electron beam exposure on the basis of the design data, executes:
- reading the shape of the light exposure pattern from the light exposure pattern storage unit;
- reading the shape of the electron beam exposure pattern from the electron beam exposure pattern storage unit;
- extracting difference information representing a difference portion between the shape of the light exposure pattern and the shape of the electron beam exposure pattern;
- and
- changing the design data for modifying shape into the shape of the light exposure pattern in accordance with the difference information.