With an intention to improve picture quality without increasing the overall number of times of data collection and to restrain artifacts resulting from differences in noise structure between parts differing in the number of times of addition, the total number V of views is equally divided into eight, and the areas of the two ends of each V/8, where the absolute value of the quantity of phase encoding is the greatest, are reduced in the number of times of addition by 1/2 of the reference number of times N, because their contributions to picture quality is small. The remaining middle 6V/8 areas are increased in the number of times of addition by 1/2 of the reference number of times N, because their contributions to picture quality are great, and further to alleviate the non-continuity of the variations of the number of times of addition, the number of times of addition in the middle 6V/8 areas is varied so as to follow either a Hamming function or a Hanning function.