PROBLEM TO BE SOLVED: To provide a charged particle beam therapeutic apparatus capable of avoiding restrictions on the size of a ring for transportation, preventing occurrence of a large step on the outer peripheral surface of the ring after connection, and suppressing degradation of precision in an irradiation position of a charged particle beam.SOLUTION: A ring 6 disposed on the outer periphery of a gantry is segmented into plural portions in a circumferential direction R, and has plural arc-like segments that are units into which the ring is segmented. Connection parts 9 are formed at both ends in a longitudinal direction of each of the segments 7, and each connection part 9 has a jutting part 9a that juts out to the side of a connection partner. This prevents borders of adjoining segments 7 from being linearly formed over the entire width of the ring 6 at the same position in the circumferential direction on the outer peripheral surface 6a of the ring 6.
