To prevent incorporation of open air into a space facing an envelope in a housing from a penetrating protruding part of a rotation shaft, and prevent reduction of dielectric strength between the high voltage of an X-ray tube and the housing.

This houses a cathode 5 and an anode 6 in the envelope 2, houses an insulating oil in the housing 1, together with that envelope 2, and is equipped with an insulating container 9 to high-voltage insulate the envelope 2 and the housing 1. By means that one end side of the rotation shaft core direction of an anode side rotation shaft 8, which is integrally connected to the envelope 2 is penetrated and protruded outward the housing 1, and is linked and coupled with a motor 14. In a state of covering a penetrating part of the anode side rotation shaft 8 of the housing 1 and penetrating the anode side rotation shaft 8, an auxiliary casing 16 is installed. The insulating oil is housed in an auxiliary space S surrounded by the housing 1 and the auxiliary casing 16, and in the penetrating part of the anode side rotation shaft 8 of the housing 1 and the auxiliary casing 16, first and second oil seals 17, 18 for preventing outward leakage of the insulating oil are interposed.