The width of respective evaluation pattern transferred using a test photomask (11) is calculated by a first calculating means (12) based on the relation with the open area ratio of a flare generation pattern, distribution of the width of respective transfer patterns thus calculated is subjected to linear approximation by a second calculating means (13) and then its inclination is calculated. Furthermore, a correction amount is varied from pattern to pattern by a correcting means (14) based on a table defining the inclination (dimensional variation) of the width of respective transfer patterns. Dimensional variation due to local flare can thereby be calculated more accurately and corrected with high accuracy.
