A circular accelerator that accelerates charged particles orbiting along an orbital path to a predetermined energy to perform, by deviating the path from the orbital path to an extraction path, extraction of the charged particles exceeding a stable region formed by multipole electromagnets (41, 42), includes a multipole electromagnet energization control unit (9) setting energization of the multipole electromagnets (41, 42) so that part of the charged particles are deviated to a discarding path other than the extraction path to discard unwanted charged particles, and then setting energization of the multipole electromagnets (41, 42) so that the charged particles orbiting in the orbital path are deviated to the extraction path to perform extraction of the charged particles.
