A particle beam rotational irradiation apparatus includes: a frame that supports an irradiation nozzle and rotates an irradiation-nozzle support member that is provided on an inner-circumference side of the frame and supports the irradiation nozzle a movable floor that has a roller movable in a circumferential direction centering on a rotation axis of the frame and a movable-floor rail that is provided in the circumferential direction on the inner-circumference side of the frame and supports the roller wherein the irradiation-nozzle support member and the movable floor have respective coupling portions that are attachable/detachable to/from each other in the circumferential direction centering on the rotation axis of the frame.
