In a scan measurement in which a mass scan is repeated across a predetermined mass range, when a voltage is returned from a termination voltage of one scan to an initiation voltage for the next scan, an undershoot or other drawbacks occur to destabilize the voltage value. Therefore, an appropriate waiting time is required. Conventionally, this waiting time has been set to be constant regardless of the analysis conditions. On the other hand, in the quadrupole mass spectrometer according to the present invention, the mass difference ΔM between the scan termination mass and the scan initiation mass is computed based on the specified mass range, and a different settling time is set in accordance with this mass difference. When the mass difference ΔM is small and hence requires only a short voltage stabilization time, a relatively short settling time is set. This shortens the cycle period of the mass scan, which increases the temporal resolution.