Provided is an X-ray source including a vacuum closed tube. The X-ray source includes a high voltage connection module, a tube module, and a magnetic lens system into which the tube module is inserted. The tube module includes a vacuum closed tube. The vacuum closed tube includes a cathode electrode provided at one end thereof, a nano-emitter on the cathode electrode, an anode electrode provided at the other end, and a first insulation spacer provided between the cathode electrode and the anode electrode. In addition, the vacuum closed tube includes a first conductive tube and a second conductive tube both provided between the cathode electrode and the anode electrode and separated from each other by the first insulation spacer, and a first collimator block covering an inner surface of the first insulation spacer and having a first opening.