X-ray tube

An X-ray photographing apparatus comprising:

• an X-ray tube comprising:
• a cathode emitting electrons;
• an anode accelerating emitted electrons;
• a target with which accelerated electrons collide and thereby generate X-rays;
• and
• an X-ray shielding member disposed so as to surround a surface of the target facing the cathode, and allowing the electrons to pass through an electron passing hole toward the target,
• wherein separately from an opening of the electron passing hole facing the cathode, the X-ray tube has a gas exhaust path allowing communication between the inside and outside of the electron passing hole;
• an X-ray detecting unit that detects X-rays emitted from the X-ray tube and passing through a subject;
• and
• a control unit that controls the X-ray tube and the X-ray detecting unit in a coordinated manner.