The present invention includes amount-of-change specifying means that specifies, among a plurality of pieces of image data generated by detection means in accordance with a detection result of radiated rays that have passed through a subject, the amount of change in a relative position of the subject with respect to the detection means during a period from a generation timing of immediately preceding image data, which is generated immediately before target image data, to a generation timing of the target image data, amount-of-radiated-rays setting means that sets the amount of radiated rays with which irradiation means performs irradiation in accordance with the amount of change, composition ratio determination means that determines a composition ratio in accordance with the amount of change, and noise reduction means that reduces noise of the target image data by combining, in accordance with the composition ratio, image data generated before the target image data with the target image data.
