A particle irradiation system includes three or more scanning magnets that scan a beam in a vertical direction (first direction) or a horizontal direction (second direction) perpendicular to each other. The three or more scanning magnets are configured such that the scanning magnets and the scanning magnets for scanning in the same direction between the vertical direction or the horizontal direction, are disposed in series on a progressing direction axis of a beam, and a volume of a magnetic field feeding region decreases as the scanning magnet is installed at a position farther from an isocenter on the progressing direction axis.
