Local flare correction at the time of exposure in the fabrication of a semiconductor device, wherein the substantial open area ratio, for each area to be exposed, to the pattern of each area is calculated and then the correction amount of flare of the pattern in each area is corrected depending on the substantial open area ratio of each area and the exposure conditions. Effect of local flare on a pattern being exposed in photolithography is thereby corrected quantitatively in conformity with the exposure conditions and an expected pattern can be formed readily and accurately.
