A pattern generation method for generating a pattern of a cell used to generate a pattern of a mask using a computer, includes obtaining data of pattern of the cell, calculating image of the pattern of the cell to obtain an evaluation value of the image by repeatedly changing a parameter value of an exposure condition when the mask which has the pattern of the cell is illuminated to project image of the pattern of the cell onto a substrate to expose the substrate, and a parameter value of the pattern of the cell, and determining parameter value of the pattern of the cell when the evaluation value satisfies a predetermined evaluation standard.