In order to obtain a particle beam irradiation apparatus that enlarges the dose distribution of beam spots while suppressing a decrease of the maximum available range of a charged particle beam, the particle beam irradiation apparatus includes a particle beam acceleration means particle beam transport means scanning apparatus that includes first scanning means and second scanning means, and two-dimensionally scans the beam and irradiation control means that controls the scanning apparatus so as to irradiate the beam onto a target region including a plurality of small regions. The irradiation control means controls the first scanning means so as to scan the beam over a small region serving as an irradiation subject among the plurality of the small regions, and controls the second scanning means so as to change the small region serving as the irradiation subject to be a different small region among the plurality of the small regions.
