Provided is an X-ray tube, including: an electron-beam emitting unit; a target having a first surface and a second surface; a solid heat diffusion member fixed onto the second surface of the target; and a flow-path forming member, which is arranged on a side of the solid heat diffusion member, the side being opposite to the target, and that is configured to define a film flow path in which a cooling fluid forms a film flow that is parallel to a surface shape of the solid heat diffusion member. A protruding portion protrudes toward the side of the solid heat diffusion member, which is opposite to the target. The film flow path has a shape extending along at least a part of a surface of the protruding portion.