A particle beam irradiation apparatus radiates a particle beam plural times per one irradiation position. A storage unit stores a dose to be radiated each of the times (divisional target dose). A dose monitor measures the dose of the particle beam radiated to the irradiation position. At the first time of radiation, a controller outputs an interruption signal when the dose measured by the dose monitor reaches the divisional target dose. The dose monitor measures a dose (excessive dose) radiated after the interruption signal is outputted until the particle beam is actually interrupted. Then, it is defined: Corrected Dose value=Divisional Target Dose−Excessive Dose Value. Instead, it may be defined: Corrected Dose value=Divisional Target Dose−Excessive Dose Estimation Value. At the second time of radiation, the controller outputs an interruption signal when the dose measured by the dose monitor reaches the corrected dose value.
