X-ray tube

The invention relates to and discloses an X-ray tube that is used for preventing the intensity of X-rays from changing along with passing of the time in a planar X-ray tube. The X-ray tube (1) includes a radiopaque substrate (4) including a window portion (3), an X-ray transmission window (8) closing the window portion, an X-ray target (9) provided at the window portion from an inner surface side of the substrate, a highly-evacuated container portion (5) attached to the inner surface of the substrate, a cathode (11), a first control electrode (12) and a second control electrode (14) provided inside the container portion. A shielding electrode (20) is provided at the inner surface of the substrate so as to surround the window portion. Electrons collide with the X-ray target to generate X-rays. Electrons reflected on the X-ray target between the shielding electrodes are absorbed by the shielding electrodes, so an inner surface of the container portion is not charged. The electron emission from the cathode is no