Patent ID: 8466428

Claim:
A particle beam irradiation apparatus that irradiates a charged particle beam accelerated by an accelerator onto an irradiation subject, the particle beam irradiation apparatus comprising: a ridge filter having a thickness distribution in which energy that the charged particle beam loses differs depending on the position thereon through which the charged particle beam passes; an upstream deflector that is disposed at an upstream side of the ridge filter and includes a first upstream deflector that deflects the charged particle beam in a direction that departs from a beam axis along which the charged particle beam enters and a second upstream deflector that is disposed at a downstream side of the first upstream deflector and deflects the charged particle beam in a direction parallel to the beam axis; a downstream deflector that is disposed at a downstream side of the ridge filter and includes a first downstream deflector that deflects the charged particle beam toward the beam axis along which the charged particle beam enters and a second downstream deflector that is disposed at a downstream side of the first downstream deflector and deflects the charged particle beam in a direction parallel to the beam axis; and a controller that controls the upstream and downstream deflectors in such a way that the charged particle beam, with a wobbling motion, passes through the thickness distribution of the ridge filter, wherein the first and second downstream deflectors deflect the charged particle beam in a same plane in which the first and second upstream deflectors deflect the charged particle beam.