A compact apparatus can form multi-X-ray beams with good controllability. Electron beams (e) emitted from electron emission elements (15) of a multi-electron beam generating unit (12) receive the lens effect of a lens electrode (19). The resultant electron beams are accelerated to the final potential level by portions of a transmission-type target portion (13) of an anode electrode (20). The multi-X-ray beams (x) generated by the transmission-type target portion (13) pass through an X-ray shielding plate (23) and X-ray extraction portions (24) in a vacuum chamber and are extracted from the X-ray extraction windows (27) of a wall portion (25) into the atmosphere.