1. A mask-layout creating method for generating a mask layout in which an auxiliary pattern is formed with respect to a design layout, the mask-layout creating method comprising: setting a design layout highly likely to be a dangerous point in a lithography process; setting, with respect to the set design layout, a coherence map kernel for generating the mask layout; creating, based on the set coherence map kernel and the set design layout, a coherence map; extracting the auxiliary pattern from the created coherence map, shaping the auxiliary pattern, and generating the mask layout; defining a cost function for evaluating an optimization degree of the mask layout and evaluating the optimization degree of the generated mask layout using the cost function; and changing, by a computer, parameters in setting the coherence map kernel to improve the evaluated optimization degree.