X-ray tube

An X-ray tube comprising:

• an electron gun that emits electrons;
• a target that generates X-rays when electrons emitted from the electron gun are incident on the target;
• and
• a vacuum housing that accommodates the electron gun and the target,
• wherein the vacuum housing has a metal portion which has an X-ray emission window emitting X-rays to the outside and a valve portion which is formed of an insulating material and is connected to the metal portion,
• wherein the metal portion has a first part in which the X-ray emission window is provided and which surrounds a central axis of the vacuum housing, and a second part which is connected to an end portion of the first part on the valve portion side, surrounds the central axis, and protrudes such that a connection part between the metal portion and the valve portion is covered, and
• wherein the second part has a shape increased in diameter such that a separation distance between a distal end portion on a side opposite to a base end portion connected to the first part and the central axis is longer than a separation distance between the base end portion and the central axis.