Time-of-flight mass spectrometer and tuning method for the same

A tuning method for a time-of-flight mass spectrometer having a measurement unit which includes a flight-field creation section configured to create, within a flight space, an electric field for causing ions to fly, and an ion acceleration section configured to accelerate ions which are a measurement target and to send the ions into the flight space, the tuning method comprising:

• a data-analysis processing step for creating a spectrum based on data acquired by the measurement unit, the spectrum showing a relationship between ion intensity and time of flight or mass-to-charge ratio;
• an index calculation step for calculating, as an index concerning a peak observed in the spectrum, a difference in time of flight or mass-to-charge ratio between a midpoint of a first peak width at an intensity which equals a top intensity of the peak multiplied by a first ratio and a midpoint of a second peak width at an intensity which equals the top intensity of the peak multiplied by a second ratio which is smaller than the first ratio;
• and
• a tuning step for tuning a voltage applied to an electrode included in the measurement unit, using at least either the index or another numerical value derived from the index.