Noise originating from the difference between a second dose as an X-ray dose used for simulation and a first dose as an X-ray dose associated with raw data obtained by past imaging operation is calculated. Simulation pure raw data as information associated with a photon count and noise which are predicted to be detected by a plurality of X-ray detection elements when imaging is performed by using X-rays of the second dose is generated on the basis of the calculated noise and the raw data obtained by past imaging operation. A simulation image predicted to be obtained by imaging operation using X-rays of the second dose is generated by using the simulation pure raw data and displayed.