Abstract: Provided is a time-of-flight mass spectrometer including: an ionization part receiving electron beams to thereby emit ions; a cold electron supply part injecting the electron beams to the ionization part; an ion detection part detecting the ions emitted from the ionization part; and an ion separation part connecting the ionization part and the ion detection part, wherein the cold electron supply part includes a microchannel plate receiving ultraviolet rays to thereby emit the electron beams, the ions emitted from the ionization part pass through the ion separation part to thereby reach the ion detection part, and the ion separation part has a straight tube shape.