An MS/MS spectrometric analysis method obtains throughput and mass resolving power of precursor ions. In a mass spectrometer, ions, which are introduced and accumulated in an ion trap unit, are resonance-extracted mass-selectively. A profile of precursor ions at the m/z axis of the ion trap and a profile at the mass analyzer portion, which performs mass analysis of the ions extracted from a collision induced dissociation portion, is obtained by performing a measurement when the injection energy to the collision induced dissociation portion is low, and when the injection energy to the collision induced dissociation portion is high. The profile at the m/z axis of the ion trap of the obtained two-dimensional spectrum is substituted with the profile at the m/z axis of the mass analyzer portion. In this way, the m/z of both the precursor ions and the fragment ions can be determined with high mass resolving power.