A function/process of recording marker position data and spot data is provided. The marker position data includes position information of a marker 29 measured for tumor tracking irradiation and information on time of execution of X-ray imaging. The spot data includes information on time of irradiation of each spot, a delivered irradiation position, and a delivered irradiation amount. The marker position data and the spot data are synchronized based on the time information, and by using the marker position data and the spot data upon spot irradiation, a delivered dose distribution of proton irradiation is calculated. With this configuration, it is possible to take the influence of interplay effect into consideration, and it is possible to support to make more appropriate determination upon replanning of a treatment plan.
