In one embodiment, a flare correction method is disclosed. The method can acquire a flare point spread function. The method can calculate a pattern density distribution in a first region of the mask, the distance from the pattern being equal to or shorter than a predetermined value in the first region. The method can calculate pattern coverage in a second region of the mask, the distance from the pattern being longer than the predetermined value. The method can calculate a first flare distribution with respect to the pattern by performing convolution integration between the flare point spread function corresponding to the first region and the pattern density distribution. The method can calculate a flare value corresponding to the second region by multiplying a value of integral of the flare point spread function corresponding to the second region by the pattern coverage. The method can calculate a second flare distribution by adding the flare value to the first flare distribution. In addition, the method can correct the pattern based on the second flare distribution.