To enable comparative observation of a plurality of animation images different in cyclicity by a method wherein at least a limited number of image signal frames out of at least cyclical first and second signals of one cycle with a different number of frames are corrected to be gradually increased to a greater number and both the signals are displayed.

When a plurality of images or abnormal images and normal images of the same patient or different patients are to be displayed simultaneously, comparative study is difficult if the number of frames per cycle, for example, the cycle of heart beating differs. To solve the problem, for example, correction files 71' are arranged with the number of frames equal to that of a second file 72 between a first image file 71 made up of frames 1-40 and the second image file 72 made up of a frame 160. Thus, the number of frames of the first image is corrected to that of the second image and a correction image signal is simultaneously displayed with the second image, thereby enabling comparative observation of a plurality of images different in cyclicity.