The present invention makes it possible to reliably verify irradiation with a particle beam in accordance with a selected irradiation technique. A particle beam therapy system includes a charged particle beam generator accelerating the particle beam, an irradiator irradiating a target with the particle beam accelerated by the charged particle beam generator, and a controller controlling the charged particle beam generator and the irradiator. The controller controls the charged particle beam generator and the irradiator so as to irradiate the target with the particle beam through switching between at least two different irradiation techniques, and furthermore, after switching between the two irradiation techniques, controls the charged particle beam generator and the irradiator to perform tentative irradiation with the charged particle beam in accordance with one of the irradiation techniques switched, to verify the particle beam.
