Abstract: A method of extracting a strong, charged particle beam, that is, a large current from an accelerator, and an accelerator capable of carrying out the method utilizes charged particles which are extracted from the accelerator. The equilibrium orbit of charged particles in one of a bending magnet and a magnet having multipole components greater than sextuple components, is shifted by a constituent element of the accelerator other than these magnets, to change the tune of charged particles. The adjustment of this tune based upon the shift of the equilibrium orbit in the above magnet for extracting charged particles, can keep the gradient of orbit of the extracted beam substantially constant. Accordingly, beam extraction is readily controlled, and a large current can be extracted from the accelerator.