TWI843499B

A particle beam irradiation apparatus includes: an accelerator accelerating a particle so as to generate a particle beam; an irradiation unit irradiating an irradiation target with the particle beam; a transport path provided between the accelerator and the irradiation unit and provided so as to be capable of transporting the particle beam; and a collimator device having a first shielding member provided in the transport path, shielding the particle beam, and having a first opening allowing the particle beam to pass in an advancing direction of the particle beam and a second shielding member provided in the transport path, shielding the particle beam, and having a second opening allowing the particle beam to pass in the advancing direction of the particle beam, in which the second shielding member is spaced from the first shielding member to a downstream side in the advancing direction of the particle beam.