PURPOSE: To contrive the reduction of cost by vertically deflecting an electron beam by using a deflecting magnet after making the electron beam incident on an accelerating tube arranged horizontally and applying phase modulation by using a microwave.

CONSTITUTION: An electron beam from an electron gun 2 is preliminarily accelerated by an electron gun power source 1 and made incident in a pre-chamber 20. Next, phase modulation is applied on the electron beam by the power of a microwave which is divided by a power divider 23 and the phase and the power of the microwave which is supplied in the pre-chamber 20 by a phase attenuator 22 are regulated. Next, the electron beam which is made incident in an accelerator 4 is accelerated to be a narrow beam, turned round at approximately 270°, deflected at a right angle to an accelerating beam line, a deflecting electron beam 26 is introduced in a deflecting duct 25, scanned by a scanning magnet 7 and used for irradiation. Therefore, the height is held low and the device can be cheap.