An X-ray generator, an X-ray inspector and an X-ray generation method capable of automatically focusing an energy beam, such as an electron beam for generating an X-ray, on a target are provided. The generation, inspector and the method have been developed by turning an attention on the fact that convergence conditions of an electron beam has a close relationship with a temperature on a surface of an X-ray tube target. The method comprises the steps of measuring the temperature changes at real time by a temperature sensor 14 and automatically controlling a current value of a focusing coil 6.