The present invention relates to a structure of an X-ray source which can reduce production costs and a defect rate. The X-ray source includes a cathode and an emitter unit which is located on one side of the cathode and emits an electron beam. The emitter unit comprises an emitter substrate and an emitter formed on the emitter substrate. The emitter substrate is mechanically fixated to the cathode. The X-ray source can simplify a process for manufacturing the X-ray source by skipping a brazing process or a welding process for attaching the cathode to the emitter as the cathode is mechanically joined to the substrate on which the emitter is formed. In addition, process costs can be reduced because an aligning microscope and a welding device, needed for the brazing or welding process, are not used as the brazing or welding process for attaching the cathode to the emitter is skipped.
