A computer-readable recording medium recording a mask data generation program, which causes a computer to generate data of a mask illuminated by illumination light and used to form a latent image on a photoresist via a projection optical system. The program causes the computer to execute a map generation step of Fourier-transforming a function indicating an effective light source to generate a coherence map expressing a coherence distribution on an object plane of the projection optical system, on which the mask is arranged, a specifying step of specifying a reference vector from an origin of the coherence map to a region where coherence is less than a reference value, a first data generation step of selecting one element from a pattern including a plurality of elements, and removing, from the pattern, an element existing at a position matching a terminal point of the reference vector arranged such that the center of the selected element serves as a starting point, to generate data of a first pattern different from the pattern, and a second data generation step of generating data of a second pattern including the element removed in generating the data of the first pattern.