To provide a rotating anode X-ray tube 11 capable of improving cooling efficiency of an anode target 18 by heat conduction, and inputting larger power to the anode target 18.

Gaps 23, 24 capable of retaining liquid lubricant 22 are provided between an inner face of a vacuum envelope 12 and a rotating anode target 18, and the liquid lubricant 22 is made to intercalate in the gaps 23, 24. Heat of the anode target 18 is directly conducted to the vacuum envelope 12 through the liquid lubricant 22. Each bearing part 25, 26 bearing the anode target against the vacuum envelope 12 in free rotation is formed by the vacuum envelope 12, the anode target 18, and the liquid lubricant 22.