Provided is a charged particle irradiation system and a charged particle irradiation method capable of shortening the irradiation time and the treatment time by performing efficient irradiation even when irregular variation occurs in the irradiation object during the gating irradiation. The extraction of the beam is stopped upon reception of a regular extraction permission end signal which is outputted based on a regular movement signal. Meanwhile, an extractable state maintaining function 46b operates upon the reception of the extraction permission end signal. When a preset standby time elapses without receiving an extraction permission start signal again during the standby time, the extractable state maintaining function 46b finishes its operation and a charged particle beam generator 1 decelerates the beam. There are also cases where the extraction of the beam is stopped due to reception of an irregular extraction permission end signal during the irradiation. Meanwhile, upon the reception of the extraction permission end signal, the extractable state maintaining function 46b operates and the charged particle beam generator 1 maintains the extractable state. When the extraction permission start signal is received again during the standby time, the extraction of the beam is restarted.
