QUADRUPOLE MASS SPECTROMETER

PROBLEM TO BE SOLVED: To provide a low-cost quadrupole mass spectrometer so arranged that an ion can be guided from an ion source to a quadrupole section efficiently.SOLUTION: A quadrupole mass spectrometer includes: a sensor part MA which has an ion source 4 having a filament 43 and a grid 41, a quadrupole section 3, a focus electrode 5 provided between the ion source and the quadrupole section, and an ion detection section 2 for capturing an ion having passed through the quadrupole section by applying a DC voltage and AC voltage between opposing electrodes; and a control unit C which has a power supply E1 for supplying DC current to the filament, a power supply E2 for applying a voltage to make the grid higher than the filament in potential, a power supply E4 for providing the filament with a potential to make a potential difference between the grid and filament, a power supply E3 for applying AC voltage with DC voltage superposed thereon to the quadrupole section, and a control section C1. In the quadrupole mass spectrometer, the filament and the focus electrode are at the same potential.