When a repeatedly periodically moving site of a to-be-examined subject in a gantry is subjected to computed tomography and is reconstructed, the gantry is rotated in synchronization with the movement of the periodically moving site, and a dynamic image showing a transient phenomenon is obtained in which the periodic movement of the moving site has been stopped. As a result, the flow of a contrast agent or the like can be observed in a state of stopping the movement of an internal organ that moves repeatedly periodically.