1. A charged particle irradiation system comprising: an accelerator for extracting a charged particle beam; charged-particle-beam scanning equipment; and a charged-particle-beam-position monitor system, wherein said charged particle irradiation system further includes a control unit for calculating a beam position at a target position on the basis of a signal received from the charged-particle-beam-position monitor system to control the charged-particle-beam scanning equipment so that the charged particle beam is moved to a desired irradiation position at the target position, and wherein in each predetermined cycle of the accelerator, said control unit corrects the value of an excitation current applied to the charged-particle-beam scanning equipment on a specified cycle basis on the basis of information about the position and the angle of the charged particle beam.