Provided is an X-ray tube which can perform stable X-ray radiation under a desired condition in a radiation region extending in a predetermined direction. Included are a base plate having an opening portion and made of alloy 426, an X-ray transmission window made of titanium foil and arranged to close the opening portion of the base plate, a flat box-like vessel portion attached to the base plate and inside of which is in a vacuum state, an X-ray target provided at the opening portion in the vessel portion, and an electron source injecting electrons to the X-ray target in the vessel portion. The electron source includes a liner cathode, a first control electrode pulling out electrons from the cathode and a second control electrode restricting radiation range of the pulled-out electrons. At this time, X-rays emitted from the X-ray window spreads radially from opening shape of the opening portion.