Mass spectrometer

A mass spectrometer having one or more ion transport optical elements each of which includes a plurality of electrodes arranged so as to surround an ion optical axis between an ion source that generates ions derived from a sample component and a detector which detects ions separated according to a mass-to-charge ratio, and transports ions while converging the ions by an effect of a radio-frequency electric field formed by the plurality of electrodes, the mass spectrometer comprising:

• a) a direct-current voltage generator configured to apply direct-current voltages of different polarities to electrodes adjacent to each other around the ion optical axis included in at least one of the one or more ion transport optical elements;
• and
• b) a controller configured to control an operation of the direct-current voltage generator so as to apply a predetermined direct-current voltage to each of the plurality of electrodes included in the at least one of the one or more ion transport optical elements from the direct-current voltage generator during a measurement preparation period during which no measurement is substantially performed between one measurement and a next measurement, and stop application of the direct-current voltage during a measurement period during which a measurement is performed.