According to the embodiments, a first representative point is set on outline pattern data on a pattern formed in a process before a processed pattern. Then, a minimum distance from the first representative point to a peripheral pattern is calculated. Then, area of a region with no pattern, which is sandwiched by the first representative point and the peripheral pattern, in a region within a predetermined range from the first representative point is calculated. Then, it is determined whether the first representative point becomes a processing failure by using the minimum distance and the area.