Abstract: A design width is changed in such a way that the design width is equal to a half-width of an exposure intensity distribution obtained by estimating a surface integral of a forward-scattering term of a basic exposure intensity distribution function over a pattern of interest. Proximity effect correction is performed such that Qcp times a sum of a half of a peak intensity of a forward-scattering component and a backscattering component is equal to the threshold value Eth for development. An exposure intensity distribution due to the backscattering term is calculated using a pattern area density method. An exposure pattern arranging plane is partitioned into meshes each for an auxiliary exposure shot whose size is smaller than that of a block shot. Auxiliary exposure is performed on each mesh short of exposure intensity after a block shot is applied.