According to one embodiment, an X-ray tube assembly includes a cathode, an anode target, a joint including an inflow part into which a coolant flows, a first cylindrical pipe to which the joint is connected at one end, and the anode target is joined at an outer bottom part of the other end, a second cylindrical pipe whose first end part is fitted into the inflow part, and whose second end part is arranged to eject the coolant toward the bottom part of the first cylindrical pipe, the second cylindrical pipe being placed inside the first cylindrical pipe and an elastic member provided between the first end part and the first cylindrical pipe.