QUADRUPOLE MASS SPECTROMETER

PROBLEM TO BE SOLVED: To provide a low-cost quadrupole mass spectrometer without the need for separate power sources, in which a grid can be degassed efficiently by electron impact.SOLUTION: The quadrupole mass spectrometer comprises: an ion source 4 having a filament 42 and a grid 41; a quadrupole part 3 with four columnar electrodes laid out at given intervals along a circumferential direction; and an ion detection part 2 for collecting predetermined ions having passed through the quadrupole part. The spectrometer further includes: a power source E1 for passing a DC current through the filament; a power source E2 for applying a potential higher than that of the filament to the grid; a power source E4 for supplying the filament with a given potential in order to create a given potential difference between the grid and filament; a power source E3 for applying, to pairs of opposing electrodes of the quadrupole part, voltages formed by positive and negative DC voltages each having AC voltage superposed thereon; and a control unit C. The power source for the quadrupole part applies, on the grid, a voltage corresponding to the potential difference between the positive and negative voltages.