In an X-ray tube 1A that makes electrons emitted from an electron gun 17 into a target 9 of an anode 8 arranged in a tubular vacuum enclosure body 6, and extracts the X-rays through an X-ray exit window 18, the anode 8 is arranged on a tube axis C1 of the vacuum enclosure body 6, and in a sealing portion 5g provided at an end portion of the vacuum enclosure body 6, provided is the X-ray exit window 18 eccentric with respect to the tube axis C1 of the vacuum enclosure body 6.