In an X-ray tube, a rotary anode formed into a hollow disk-like shape is fixedly supported by a rotating body formed into a hollow cylindrical shape. A fixed shaft has fixed ends, columnar bearing portions and a disk part, and a flow path of a cooling medium formed along a central axis thereof. The bearing portions are inserted into the rotating body with a first gap between the columnar bearing portion and the rotating body, so that the rotating body is rotatably supported. The disk part is arranged in the rotary anode with a second gap between the disk part and the rotary anode. The first and second gaps are filled with a lubricant, bearing grooves are formed in the bearing portion, thereby forming dynamic pressure bearings, and a center of gravity of the rotary anode is arranged between the first and second dynamic pressure bearings.