PROBLEM TO BE SOLVED: To provide a thoracic part kinetics image in which a signal change by moving of structures, such as a bone part is removed without making a complicated device constitution, and which is easy to observe a density change of a lung field tissue.SOLUTION: According to a diagnosis console 3, a control part 31 extracts a structure area which shows a predetermined structure from each of two or more frame images which show kinetics of a thoracic part, and presumes a signal variation by moving of the structure between frames based on a signal value in the extracted structure area of the adjoining frame images. Moreover, the alignment of a lung field area between two or more frame images is performed, a difference image between frames is formed by taking the difference of a signal value of a pixel which corresponds between frame images which adjoin in time. In addition, when a signal variation between presumed frames is over a threshold defined beforehand, a signal value of an area corresponding to an extracted structure area in a difference image between frames is rectified.
