Abstract: A charged particle accelerator capable of accelerating arbitrarily charged particles to an arbitrary energy level and resonating at a low frequency suitable for accelerating heavy ions, including quadruple electrodes which are supplied with high frequency power and disposed in the direction of the center axis of a cylinder-shaped container and a resonant circuit having a capacitor and an inductor for supplying a voltage to the quadruple electrodes. The capacitor is composed of a plurality of metallic plates provided along the center axis at specified intervals in the vicinity of the quadruple electrodes, and a plurality of conductive supports supporting the metallic plates which are directly connected to the container together with the supports and the container form the inductor.