A treatment planning apparatus of the present invention comprises a processor configured to predict a degree of sharpness of an X-ray image which is acquired with assumed X-ray intensity and calculate position uncertainty of an affected area, calculate irradiation parameters of a therapeutic radiation based on the calculated position uncertainty of the affected area, calculate an X-ray irradiation amount with which a patient is irradiated by an X-ray imaging device with the assumed X-ray intensity and calculate a dose distribution of the therapeutic radiation which is irradiated to the patient using the calculated irradiation parameters of the therapeutic radiation and a display that displays the calculated X-ray irradiation amount and the calculated therapeutic radiation dose distribution.
