Abstract: A dose monitor measures a dose of a beam. The position monitor measures the beam size of the beam. The irradiation control apparatus calculates the measurement characteristic of the dose monitor based on the dose and the beam size of the beam, and controls the irradiation of the patient with the beam based on the measurement characteristic and the dose.

Abstract: A correlation between a CT value and a water equivalent thickness ratio distribution for each patient can be corrected without increasing a treatment time, and more accurate treatment can be realized. A treatment planning system 112 which generates a treatment plan for irradiating an irradiation target with a particle beam calculates a correction amount of a water equivalent thickness ratio of a first treatment plan created in advance, calculates a water equivalent thickness ratio distribution based on the correction amount and the first treatment plan, and creates a second treatment plan from the water equivalent thickness distribution.