To provide an accelerator, a power storage apparatus and a launcher suitable for obtaining a large energy in terms of cost.

The accelerator for accelerating an accelerating medium 10 in an annular accelerating tube 400 comprises a deflector 420 for deflecting the circumferential orbit of the medium 10 along the orbit of the tube 400 by a magnetic attraction or repulsion force, and an accelerating part 450 for accelerating the medium 10 by the magnetic attraction or repulsion force. In the part 450, accelerating electromagnets 22, 24 are provided along the inner peripheral surface of the tube 400, disposed along the extending direction of the tube 400. In this case, before the medium 10 is passed through the magnet 22, the magnet 22 is magnetized so as to become an opposite polarity to that of the pole of the medium 10. Thus, become the medium 10 passes the electromagnet 24, the electromagnet 24 is magnetized so as to become the opposite polarity to that of the pole of the medium 10, thereby accelerating the medium 10.