This invention improves the sensitivity of a liquid chromatography-mass spectrometry device by reducing the number of neutral particles that are not ionized during ionization and the number of low-molecular ions from a solvent used in the liquid chromatography. Said liquid chromatography-mass spectrometry device is provided with ion sources (102, 104, 120, 121), a mass spectrometry unit, a detector, and three electrodes (105, 106, 107) laid out so as to be parallel to each other. The first electrode (105) and the second electrode (106) have openings (122, 123) that allow ions to pass therethrough. The trajectories of said ions are deflected between the second electrode (106) and the third electrode (107), thereby directing ions generated by the ion sources (102, 104, 120, 121) towards the mass spectrometry unit.