When a beam acceleration high frequency control section turns on an accelerating cavity in synchronization with a beam irradiation on state, the beam acceleration high frequency control section rapidly increases an amplitude value of an applied voltage of the accelerating cavity. The control section rapidly decreases the amplitude value of the applied voltage of the accelerating cavity before beam irradiation off timing. When the control section turns off the accelerating cavity, the control section gradually decreases the amplitude value of the applied voltage of the accelerating cavity before the irradiation off timing. When the control section turns on the accelerating cavity and starts the beam irradiation, the control section gradually increases the applied voltage of the accelerating cavity.
