To ensure irradiation accuracy and safety, even when an irradiation device employing a different irradiation method is used, disclosed is herein a charged particle beam irradiation apparatus that irradiates an irradiation target with charged particle beams includes: a charged particle beam generator for generating the charged particle beams; a passive scattering irradiation device and a scanning irradiation device, both for irradiating the irradiation target with the charged particle beams; a beam transport system for transporting the charged particles beam extracted from the charged particle beam generator, to selected one of the two irradiation devices; and a central controller that modifies operating parameters on the charged particle beam generator, according to the irradiation method adopted for the selected irradiation device.