1. A mass spectrometer capable of an MS n analysis (where n is an integer greater than two), which is characterized by comprising: a) a mass spectrum creating means for creating an MS m-1 spectrum (where m is an integer greater than two and no greater than n) based on mass analysis data obtained by an MS m-1 analysis performed for each of first and second components; b) a mass-difference spectrum creating means for calculating, for each of the two MS m-1 spectrums, a mass difference between a mass of each peak among some or all of peaks appearing on the MS m-1 spectrum and a mass of a precursor ion, and for creating an MS m-1 mass-difference spectrum having a peak at each of the calculated mass differences; c) a common-peak extracting means for extracting a peak having a same mass in the two MS m-1 mass-difference spectrums relating to the first component and the second component; d) a complementary-peak extracting means for extracting a complementary peak on the MS m-1 spectrum relating to the first component and/or the second component, the complementary peak corresponding to a mass difference between the mass of the precursor ion and the mass of the common peak; and e) an analysis control means for conducting an MS m analysis so that the first component and/or the second component is subjected to an m−1-th stage of a dissociation operation with an ion corresponding to the complementary peak designated as the precursor ion.