A high-quality mass spectrum is provided with alleviated mass/charge axis deviation in a triple quadrupole mass spectrometer even when executing a high-speed mass scan with MS/MS analysis. Mass calibration tables which denote relations between m/z and a mass deviation value which scan speed is a parameter are prepared separately for use in MS analyses without involving dissociation operations and MS/MS analyses with involving dissociation operations. According to a measuring mode, such as a product ion scan measurement or a neutral loss scan measurement, when performing MS/MS analysis, a mass deviation value for the minimum scan speed in a table is used for a quadrupole where the selected m/z is fixed, and a mass deviation value for a designated scan speed in a table is used for a quadrupole where the mass scan is performed, thus controlling the operations of each of a pre-stage and a post-stage quadrupoles.