Mass spectrometer and method for controlling same

A mass spectrometer comprising:

• an ion source that ionizes a sample;
• a mass spectrometry unit that detects ions for each mass-to-charge ratio;
• a control unit that controls a flow rate of a gas;
• and
• a storage unit,
• wherein
• the ion source includes
• an ion source chamber,
• an inlet through which the sample is introduced into the ion source chamber,
• a first gas introduction port through which a first gas is introduced into the ion source chamber,
• a second gas introduction port through which a second gas for ionizing the sample is introduced into the ion source chamber,
• an outlet through which ions are discharged from the ion source chamber to the mass spectrometry unit, and
• a gas discharge port through which a gas is discharged from the ion source chamber,
• the storage unit stores a table indicating a relationship between a measurement condition and a flow rate of the second gas, and
• the control unit
• changes the flow rate of the second gas according to the measurement condition on the basis of the table, and
• controls a flow rate of the first gas to suppress a variation in a pressure inside the ion source chamber.