Mass spectrometer and control method thereof

A mass spectrometer comprising:

• an ionizing unit that generates ions from a sample;
• a mass filter that separates the ions according to a mass-to-charge ratio;
• and
• a detecting unit that detects the ions separated by the mass filter, wherein,
• the mass spectrometer further includes comprising:
• an ion guide that transports the ions to the mass filter;
• and
• a control unit that generates a mass spectrum and a mass chromatogram, using detection signals obtained by performing a sweep control and a step control, the sweep control for gradually increasing a high frequency voltage to be applied to the ion guide, and the step control constantly keeping the high frequency voltage, wherein
• the control unit switches from the sweep control to the step control, at a timing when the high frequency voltage gradually increased by the sweep control reaches a range in which a change of ion transmittance is small.