A charged particle irradiation apparatus configured to perform scanning with a charged particle beam and irradiate an irradiation target spot by spot, the charged particle irradiation apparatus comprising: a first dose monitor mounted in an irradiation nozzle ; an irradiation pattern converting device that generates irradiation control data used for controlling the charged particle irradiation apparatus from input of treatment plan data including information on a dose rate and a dose of a charged particle beam for each spot; and a dose correction factor storage unit that stores data of a dose correction factor R with respect to a dose rate of a charged particle beam, wherein the irradiation pattern converting device is configured to (i) select one spot in the treatment plan data, (ii) correct a dose value corresponding to the selected spot by using a dose rate, which corresponds to the selected spot and is included in the treatment plan data, as a key to acquire a dose correction factor R corresponding to the dose rate from the dose correction factor storage unit and multiplying a dose value corresponding to the selected spot and included in the treatment plan data by the dose correction factor R, (iii) perform processes of the (i) and (ii) on all of spots in the treatment plan data, and (iv) generate irradiation control data for a dose by using corrected dose data for all of spots in the treatment plan data, and wherein the charged particle irradiation apparatus corrects a difference between an actual dose delivered in an irradiation target and a dose measured by the first dose monitor, wherein the difference is caused by influence of ion recombination in the first dose monitor. a first dose monitor mounted in an irradiation nozzle ; an irradiation pattern converting device that generates irradiation control data used for controlling the charged particle irradiation apparatus from input of treatment plan data including information on a dose rate and a dose of a charged particle beam for each spot; and a dose correction factor storage unit that stores data of a dose correction factor R with respect to a dose rate of a charged particle beam, wherein the irradiation pattern converting device is configured to (i) select one spot in the treatment plan data, (ii) correct a dose value corresponding to the selected spot by using a dose rate, which corresponds to the selected spot and is included in the treatment plan data, as a key to acquire a dose correction factor R corresponding to the dose rate from the dose correction factor storage unit and multiplying a dose value corresponding to the selected spot and included in the treatment plan data by the dose correction factor R, (iii) perform processes of the (i) and (ii) on all of spots in the treatment plan data, and (iv) generate irradiation control data for a dose by using corrected dose data for all of spots in the treatment plan data, and (i) select one spot in the treatment plan data, (ii) correct a dose value corresponding to the selected spot by using a dose rate, which corresponds to the selected spot and is included in the treatment plan data, as a key to acquire a dose correction factor R corresponding to the dose rate from the dose correction factor storage unit and multiplying a dose value corresponding to the selected spot and included in the treatment plan data by the dose correction factor R, (iii) perform processes of the (i) and (ii) on all of spots in the treatment plan data, and (iv) generate irradiation control data for a dose by using corrected dose data for all of spots in the treatment plan data, and wherein the charged particle irradiation apparatus corrects a difference between an actual dose delivered in an irradiation target and a dose measured by the first dose monitor, wherein the difference is caused by influence of ion recombination in the first dose monitor. <EOS>