A particle beam therapy system (100) is capable of achieving an irradiation beam suitable for a particle beam therapy using a spot scanning method and can be realized at low cost. The particle beam therapy system (100) includes a synchrotron (200), a beam transport system (300), an irradiation system (500), and a controller (600). A controller is configured to turn on a radio frequency electromagnetic field to be applied to an extraction system when a charged particle beam is to be supplied to the irradiation system, and turn off the radio frequency electromagnetic field to be applied to the extraction system when the supply of the charged particle beam to the irradiation system is to be blocked by means of an electromagnet provided in the beam transport system or in the synchrotron (200). The controller is also adapted to turn off a radio frequency acceleration voltage to be applied to an acceleration cavity in synchronization with the turning-off of the radio frequency electromagnetic field to be applied to the extraction device (26).
