A particle beam irradiation apparatus comprising: - particle beam acceleration means that are adapted to accelerate a charged particle beam; - particle beam transport means that are adapted to transport a charged particle beam launched from the particle beam acceleration means; - a scanning apparatus (3, 4) that is adapted to scan the charged particle beam transported by the particle beam transport means and includes first scanning means and second scanning means; and - irradiation control means that are adapted to control the scanning apparatus (3, 4) so as to irradiate the charged particle beam onto a target region wherein, in a two-dimensional plane perpendicular to a direction of travel of the charged particle beam, the target region includes a plurality of small regions, - wherein the irradiation control means are adapted to control the first scanning means so as to scan the charged particle beam over a small region serving as an irradiation subject among the plurality of the small regions and control 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, characterised in that: in the scanning apparatus (3, 4), both of the first scanning means and the second scanning means are adapted to generate a deflection magnetic field or a deflection electric field in directions that are perpendicular to a traveling direction of the charged particle beam, and are each adapted to two-dimensionally scan the charged particle beam transported by the particle beam transport means, wherein the plurality of the small regions is arranged so as to have portions overlapping with one another. - particle beam acceleration means that are adapted to accelerate a charged particle beam; - particle beam transport means that are adapted to transport a charged particle beam launched from the particle beam acceleration means; - a scanning apparatus (3, 4) that is adapted to scan the charged particle beam transported by the particle beam transport means and includes first scanning means and second scanning means; and - irradiation control means that are adapted to control the scanning apparatus (3, 4) so as to irradiate the charged particle beam onto a target region wherein, in a two-dimensional plane perpendicular to a direction of travel of the charged particle beam, the target region includes a plurality of small regions, - wherein the irradiation control means are adapted to control the first scanning means so as to scan the charged particle beam over a small region serving as an irradiation subject among the plurality of the small regions and control 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, in the scanning apparatus (3, 4), both of the first scanning means and the second scanning means are adapted to generate a deflection magnetic field or a deflection electric field in directions that are perpendicular to a traveling direction of the charged particle beam, and are each adapted to two-dimensionally scan the charged particle beam transported by the particle beam transport means, wherein the plurality of the small regions is arranged so as to have portions overlapping with one another.