Provided is an X-ray generator which includes:an electron path 8; a target 9c disposed on a substrate 9a, in which electrons having passed through the electron path 8 are made to emit at the target 9c and to generate an X-ray, wherein: the target 9c is disposed at the central area of the substrate 9a; at least a part of a peripheral area of the substrate 9a which is not covered with the target 9c has higher transmittance than that of the central area of the substrate 9a covered with the target 9c, with respect to the X-ray generated when electrons having reflected from the target enter an inner wall of the electron path. X-ray generation efficiency may be improved by effectively using electrons reflected off the target 9c.