A particle beam therapy system which includes: a particle beam generation device (30) that generates a particle beam with which an affected part of a patient to be irradiated is irradiated； and an x-ray imaging device (50) that emits an X-ray to the subject being irradiated and captures an X-ray image. This particle beam therapy system has a therapy beam emittable period during which the particle beam can be emitted to the subject being irradiated, and a therapy beam non-emittable period during which the particle beam cannot be emitted to the subject being irradiated. The x-ray imaging device (50) uses a first frame rate for the imaging frame rate of the X-ray image of the subject being irradiated in an X-ray imaging period which is a period that includes at least a part of the therapy beam emittable period, and uses, in periods other than the X-ray imaging period, an imaging frame rate that is lower than the first frame rate.
