The present disclosure relates to a fabrication method of a photomask. The method of fabricating a photomask provides for a layout of patterns to be designed. The layout of patterns may be formed on a wafer on which chips are formed. The layout of patterns are corrected to provide a layout of a photoresist pattern serving as an etching mask for forming the patterns on the wafer while generating a flare map of the patterns. An optical proximity correction (OPC) may be performed at a chip level on the corrected layout of patterns to perform a secondary correction of the layout of patterns. A second OPC may be performed at a level of a shot which includes a plurality of ones of the chips by reflecting the flare map on the second corrected layout of patterns to a third corrected layout of patterns.