An X-ray tube includes: a cathode assembly that emits electrons; an anode that receives the electrons and generates X-rays; an envelope that is a case having the cathode assembly and the anode accommodated therein; a first shielding portion that shields the X-rays between the envelope and the cathode assembly on a reference line that connects a center of a point where the electrons are generated and a center of a point where the X-rays are generated; and a second shielding portion that shields the X-rays between the envelope and the cathode assembly in a direction perpendicular to the reference line from the center of the electron generation point.