To provide an easily operable X-ray generator having proper cooling efficiency for an X-ray tube and for the high-voltage generator.

This X-ray generator is provided with the X-ray tube 12 and a container housing the X-ray tube 12, and an X-ray is generated from the X-ray tube 12 by means of an electric current fed from a cable 8a. The container is filled with insulating oil, and the electric current fed from the cable 8a is increased to a high-voltage current. The light-voltage generator for application to the X-ray tube 12 is arranged inside the container, while an inlet 7 and an outlet 19 for the insulating oil connected to an oil circulation cooling means 7 are arranged in this container.