A mass spectrometer comprising an ionization region for ionizing a sample under atmospheric pressure, an ion sampling aperture for introducing ions generated by the ionization region into a vacuum, and a mass analysis region for mass analyzing the ions on the basis of a high-frequency electric field, wherein: an electrostatic lens for deflecting the direction of the movement of the ion from the center axis of the ion sampling aperture is disposed between the ionization region and the mass analysis region; the center axis of an aperture for introducing ions into the mass analysis region and the center axis of the ion sampling aperture are disposed so as to be shifted in parallel from each other; and the center axis of the ion sampling aperture and the center axis of a cylindrical inner electrode constituting the electrostatic lens are disposed so as to be shifted in parallel from each other to thereby prevent charged droplets or droplets without charge from flowing into the mass analysis region.