A particle beam irradiation apparatus which comprises: - a particle beam generation-transportation system that is configured to perform transportation and interruption of an accelerated particle beam; - a scanning device that is configured to deflect the particle beam transported from the particle beam generation-transportation system in two directions perpendicular to a traveling direction of the beam, to thereby move from one to another of irradiation positions at which an irradiation target is irradiated; - a controller that is configured to control the particle beam generation-transportation system and the scanning device; and - a dose monitor that is configured to measure a dose of the particle beam; wherein the particle beam is radiated plural times to each said irradiation position, and the particle beam is interrupted at the time the irradiation position is being moved; the particle beam irradiation apparatus including a storage unit in which positional information of the irradiation position and a divisional target dose that is a dose radiated per one time to the irradiation position, are to be stored; wherein the dose monitor, when the measured dose reaches a value of the divisional target dose, is configured to measure an excessive dose radiated from when reaching to that value until radiation of the particle beam is interrupted; wherein, at a first time of radiation to each said irradiation position, the controller is configured to control the particle beam generation-transportation system and the scanning device to repeat, for up to a last said irradiation position at a same depth in the irradiation target, an operation in which, when the measured dose with respect to one said irradiation position measured by the dose monitor reaches the value of the divisional target dose, the particle beam generation-transportation system interrupts radiation of the particle beam and the scanning device performs deflection control corresponding to a next said irradiation position and thereafter, the particle beam generation-transportation system restarts radiation of the particle beam; and wherein, at a second or later time of radiation to each said irradiation position, the controller is configured to control the particle beam generation-transportation system and the scanning device to repeat just a predetermined number of times, for every said irradiation position at a same depth in the irradiation target, an operation in which, when the measured dose with respect to one said irradiation position measured by the dose monitor reaches a corrected dose value resulted from subtracting a value of the excessive dose at a previous time at that irradiation position from the value of the divisional target dose, the particle beam generation-transportation system interrupts radiation of the particle beam and the scanning device performs deflection control corresponding to a next said irradiation position and thereafter, the particle beam generation-transportation system restarts radiation of the particle beam. - a particle beam generation-transportation system that is configured to perform transportation and interruption of an accelerated particle beam; - a scanning device that is configured to deflect the particle beam transported from the particle beam generation-transportation system in two directions perpendicular to a traveling direction of the beam, to thereby move from one to another of irradiation positions at which an irradiation target is irradiated; - a controller that is configured to control the particle beam generation-transportation system and the scanning device; and - a dose monitor that is configured to measure a dose of the particle beam;