PURPOSE: To obtain a captioned device being compact and having a good electron ray distribution property by providing one or more filaments, a scanning electrode scanning electron rays from the filaments for each filament and an acceleration means accelerating the electron rays scanned by the scanning electrode.

CONSTITUTION: One or plural filaments 1 are used while heating these for drawing out thermal electrons and scanning in advance electron rays E and B for each filament by a scanning electrode 9, thereafter accelerating the scanned electron rays E and B in order to radiate these on the objects to be irradiated through a radiation window 5. The acceleration means shall be, for instance, the radiation window 5 to be held in the potential on the earthing side to the filament 1 on the high voltage side or to the cathode electrode 12. Thereby, as the electron rays are scanned by the scanning electrode for an individual filament, a scanning tube as in the past becomes unrequired thus making the device to be small-sized and compact. Further, the electron ray distribution can be easily unified by regulating the scanning wave from outside.