To make it possible to take out electron beams in 2 directions without changing over the polarity of an electromagnet for deflection in an electron accelerator.

The electron accelerator comprises electromagnets 1 arranged in a ring form so as to create a magnetic field, the field intensity of which is inclined in a direction perpendicular to the circulating direction of an electron beam, i.e., a radial direction, and circulate the electron beam along a circular orbit, an acceleration electrode 4 for the electron beam arranged at a part of the ring, an induction iron core 5 which generates induction voltage to the acceleration electrode 4 by supply of an a.c. current, means 6a, 6b, 7 and 10 for striking an electron beam to be accelerated on the ring-like circulating orbit toward either a clockwise direction or an anti-clockwise direction, and means 9a, 9b for taking the accelerated electron beam out of the circulating orbit after a fixed period of time.