An particle beam therapy system comprises a scanning electromagnet for scanning a particle beam which travels in a vacuum duct so as to irradiate an irradiation object and an irradiation unit comprising a beam outlet window, wherein the irradiation unit is configured such that the vacuum duct can be divided by a flange surface which is provided at a position closer to an irradiation object than a scanning electromagnet, in a case where a vacuum duct for a scanning irradiation method which is provided at a position closer to an irradiation object than the flange surface is moved so as not to overlap a beam line of the particle beam, a ride filter for a broad beam irradiation method can be provided at space where the vacuum duct for a scanning irradiation method was provided before it was moved.
