Provided is a mass spectrometer which repeats the operation of capturing ions originating from a sample component into an ion trap (22), ejecting the ions from the ion trap, and analyzing the ions with a TOF mass analyzer (23). A capturing voltage generator (51) applies an ion-capturing radio-frequency voltage to the ion trap. An ejecting voltage generator (52) applies an ion-ejecting voltage whose phase is synchronized with the radio-frequency voltage. A controller (4) controls those devices to introduce next ions to be analyzed into the ion trap while performing a mass spectrometric analysis in the TOF mass analyzer. A blank signal acquirer (4, 32) acquires a blank signal within a measurement period or measurement window while the ion trap is being operated. A noise remover (33) subtracts blank-signal data from signal intensity data acquired by a sample measurement. A spectrum creator (34) creates a mass spectrum based on noise-removed data.