The present invention relates to a device for obtaining the ion source of a mass spectrometer using an ultraviolet diode and a CEM module, having the purpose of inducing initial electron emission using a CEM module and by radiating ultraviolet photons emitted from the ultraviolet diode to the entrance of the CEM module to obtain a large amount of amplified electron beams from the exit and to produce electron beams the emission times of which are accurately controlled at low temperature and at low power. The present invention is characterized by a device for obtaining the ion source of a mass spectrometer using an ultraviolet diode and a CEM module, the device consisting essentially of: an ultraviolet diode emitting ultraviolet rays by means of supplied power; an electron multiplier inducing and amplifying the initial electron emission of ultraviolet photons from the ultraviolet diode and obtaining a large amount of electron beams from the exit; an electron condenser lens condensing the electron beams amplified by the electron multiplier; an ion trap mass separator ionizing gas sample molecules by the electron beams injected through the electron xondensing lens; and an ion detector detecting ions separated from the ion trap mass separator by mass spectrum, wherein the electron multiplier is a CEM module.