MASS SPECTROMETER

The present invention provides a mass spectrometer including a sample introduction part, an ionization part connected to the sample introduction part and configured to ionize the sample introduced from the sample introduction part, an ion lens part including an extraction lens adjacent to the ionization part and a guiding lens configured to guide ion beam extracted from the extraction lens, and a detection part configured to detect the ion beam, wherein the extraction lens has a front opening facing the ionization part, a rear opening facing the guiding lens, and a side opening between the front opening and the rear opening.