The object is to obtain a particle beam therapy system, the irradiation flexibility of which is high and that can reduce the amount of irradiation onto a normal tissue.There are provided a scanning electromagnet (2) that is adapted to perform scanning and outputting in such a way that a supplied charged particle beam Bec is formed in a three-dimensional irradiation shape based on a treatment plan and deflection electromagnets (4 and 5) that are adapted to switch the orbits for the charged particle beam Bec in such a way that the charged particle beam Bec with which scanning and outputting are performed by the scanning electromagnet (2) reaches an isocenter (C) through a single beam orbit selected from a plurality of beam orbits (7a, 7b, and 7c) established between the isocenter (C) and the scanning electromagnet (2). The distance between the scanning electromagnet and the isocenter is made long.
