Patent ID: 8754386

Claim:
A multi-leaf collimator that is disposed in a particle beam that is irradiated so as to enlarge an irradiation field of the particle beam, in order to conform the irradiation field to an irradiation subject, the multi-leaf collimator comprising: a leaf row in which a plurality of leaf plates are arranged in the thickness direction thereof in such a way that respective one end faces of the leaf plates are trued up; and a leaf plate drive mechanism that drives each of the plurality of leaf plates in such a way that the one end face approaches or departs from a beam axis of the particle beam, wherein in each of the leaf plates, a facing side facing a leaf plate that is adjacent to that leaf plate in the thickness direction is formed of a plane including a first axis that is perpendicular to the beam axis and is set at a first position on the beam axis; and wherein the leaf plate drive mechanism drives the leaf plate along a circumferential orbit around a second axis that is perpendicular to the beam axis and the first axis and is set at a second position that is on the beam axis and separate from the first position by a predetermined distance wherein the first axis coincides with a scanning axis of one of two electromagnets, and wherein the second axis coincides with a scanning axis of the other of two electromagnets.