The present invention provides an X-ray tube that improves and stabilizes a withstanding voltage performance and thus ensures the reliability of a product.The present invention is an X-ray tube comprising a cathode for emitting electrons, an anode for emitting an X-ray which an irradiation of the electrons emitted from the cathode causes, and a glass tube for confining the cathode and the anode in a vacuum, wherein an inside surface of the glass tube is covered with a glass thin film having a melting point lower than that of a glass of the glass tube and particles adhered to the glass tube by the glass thin film.