Disclosed herein is provided a particle therapy system capable of reducing an increase in treatment time caused by the initialization operation of magnets in the execution of the scanning irradiation method successively changing the energy level of a beam extracted from an accelerator 5. An irradiation control apparatus 35 has a scheme that calculates setting vales of excitation current for bending magnets 15, 20A, 20B, 20C for a transport system on every irradiation condition (energy condition), and thereby sets appropriate excitation current values according to the irradiation sequence. Specifically, the irradiation control apparatus 35 prestores in a current supply control table 1 reference current values determined corresponding to energy levels of the ion beam, prestores in current supply compensation value tables 1, 2 compensation current values determined corresponding to energy levels of the ion beam and numbers of times of changing the energy level, and calculates the excitation current value of the magnets by using the values prestored in the tables.
