In a particle beam irradiation apparatus that controls a scanning apparatus so that each irradiation position is irradiated with a particle beam a rescan-count number of times by repeating for the rescan-count number of times the irradiation of all irradiation positions in the irradiation target, the irradiation apparatus includes a calculator that receives either one of a rescan count n or a beam intensity J that is a particle beam dose per unit time, to calculate a maximum value of the other satisfying the following conditional expression (P1) for all irradiation positions to present the maximum value to a user. J*ti≦di/n  (P1)