Provided is a method for generating Mill data including applying, by an Mill computing device, an RF excitation pulse, and completing, by the MM computing device, a K-space by acquiring a plurality of phase encoding line groups, in a state in which any other RF excitation pulse is not applied after applying the RF excitation pulse, in which each of the plurality of phase encoding line groups includes a plurality of phase encoding lines, and an absolute value of an average phase encoding size of a phase encoding line group acquired earlier is not greater than an absolute value of an average phase encoding size of a phase encoding line group acquired later, among the plurality of phase encoding line groups.