Disclosed herein are provided an arrangement of devices suitable to downsize a synchrotron, a synchrotron using such an arrangement, and a particle therapy system using the synchrotron. In the synchrotron 200, a plurality of deflection magnets 202 and a single defocusing quadrupole magnet 204 are arranged between a first extraction deflector 208 and a second extraction deflector 209. The defocusing quadrupole magnet 204 is arranged between deflection magnets 202 among the plurality of deflection magnets 202, a focusing quadrupole magnet 203 is arranged on the side of an inlet of the first extraction deflector 208, and a focusing quadrupole magnet 203 is arranged on the side of an outlet of the second extraction deflector 209.
