Abstract: An initial hash database is generated by giving hash indices to drawing data of drawing patterns that are obtained by performing calculation processing on exposure data relating to layout-designed exposure data. Then, drawing data of a target drawing pattern is extracted by searching the hash database, and the extracted drawing data is subjected to a proximity effect correction. Then, a new hash database is generated by giving hash indices to the corrected drawing data. As a result, the data retrieval time is greatly shortened and the amount of corrected data is reduced.