1. A particle beam irradiation apparatus comprising: an accelerator for extracting a charged particle beam; an beam delivery apparatus having a charged particle beam scanning unit and irradiating the charged particle beam extracted from the accelerator; and a controller that stops the irradiation of the charged particle beam from the beam delivery apparatus, and that, in a state where the irradiation of the charged particle beam is stopped, controls the charged particle beam scanning unit to change the irradiation position of the charged particle beam, start the irradiation of the charged particle beam from the beam delivery apparatus after said change, and perform irradiations of the charged particle beam with respect to at least one said irradiation position a plurality of times based on treatment planning information.