PURPOSE: To obtain the effect capable of realizing radiotherapy of every kind by one apparatus, by generating both of electron beam of relatively low energy and electron beam of relatively high energy.

CONSTITUTION: The pulse generated from a pulse source 16 is sent to either one of a pulse transformer 14 and a pulse transformer 17 by a pulse change-over device 15. When the pulse is sent to the pulse transformer 14, electron beam is generated from the second electron gun 13 to be driven in an X-ray target 9. Since this electron beam is not accelerated by an accelerator, it is low energy one. The low energy X-rays generated by this low energy electron beam are allowed to irradiate the affected part while filtered by a filter 111. The high energy electron beam generated by the first electron gun 1 and an acceleration tube 3 is deflected by a deflecting electromagnet 8 to irradiate the target 9 and high energy X-rays are generated. In this case, the high energy electron beam is incident to the target 9 in an oblique direction but generates X-rays equivalently same to that in the case vertically incident to a target having the same thickness as that looked in said oblique incident direction.