A method of processing mass analysis data collected by using a mass spectrometer capable of an MS n analysis, where n is an integer greater than one, the mass analysis data being obtained by an MS n analysis on an ion having a specific mass as a precursor ion for each of at least two components inclusive of a first component and a second component having a chemical structure common to the first component, the method comprising the following steps of: a) creating a first MS n spectrum based on mass analysis data obtained for the first component and a second MS n spectrum based on mass analysis data obtained for the second component; a1) designating a first component precursor ion and a second component precursor ion; b) for each of the first and second MS n Spectra (P4, P1), firstly, calculating a mass difference between the mass of each peak among some or all of the peaks appearing on the corresponding MS n spectrum and the mass of the corresponding precursor ion, and secondly, creating a corresponding MS n mass-difference spectrum (P3, P2) having a peak at each calculated mass difference; c) extracting a first common peak in the two MS n spectra (P4, P1), having the same mass in the two MS n spectra (P4, P1) relating to the first component and the second component and/or extracting a second common peak in the two MS n mass-difference spectra (P3, P2), having the same mass in the two MS n mass-difference spectra (P3, P2) relating to the first component and the second component; d) extracting a complementary peak on one of the MS n spectrum and the MS n mass-difference spectrum relating to one of the first component and the second component, the complementary peak correspending to a mass difference between the mass of the corresponding precursor ion used in the MS n analysis for the one of the first component and the second component and the mass of the common peak on the other one of the MS n spectrum and the MS n mass-difference spectrum relating to the first component and the second component; and e) showing the one of the MS n spectrum and the MS n mass-difference spectrum on a display screen, with the corresponding complementary peak on the one of the MS n spectrum and the MS n mass-difference spectrum relating to the one of the first component and the second component, having a style visually distinguishable from that of other peaks on the MS n spectrum and/or the MS n mass-difference spectrum relating to the one of the first component and the second component. a) creating a first MS n spectrum based on mass analysis data obtained for the first component and a second MS n spectrum based on mass analysis data obtained for the second component; a1) designating a first component precursor ion and a second component precursor ion; a1) designating a first component precursor ion and a second component precursor ion; b) for each of the first and second MS n Spectra (P4, P1), firstly, calculating a mass difference between the mass of each peak among some or all of the peaks appearing on the corresponding MS n spectrum and the mass of the corresponding precursor ion, and secondly, creating a corresponding MS n mass-difference spectrum (P3, P2) having a peak at each calculated mass difference; c) extracting a first common peak in the two MS n spectra (P4, P1), having the same mass in the two MS n spectra (P4, P1) relating to the first component and the second component and/or extracting a second common peak in the two MS n mass-difference spectra (P3, P2), having the same mass in the two MS n mass-difference spectra (P3, P2) relating to the first component and the second component; d) extracting a complementary peak on one of the MS n spectrum and the MS n mass-difference spectrum relating to one of the first component and the second component, the complementary peak correspending to a mass difference between the mass of the corresponding precursor ion used in the MS n analysis for the one of the first component and the second component and the mass of the common peak on the other one of the MS n spectrum and the MS n mass-difference spectrum relating to the first component and the second component; and e) showing the one of the MS n spectrum and the MS n mass-difference spectrum on a display screen, with the corresponding complementary peak on the one of the MS n spectrum and the MS n mass-difference spectrum relating to the one of the first component and the second component, having a style visually distinguishable from that of other peaks on the MS n spectrum and/or the MS n mass-difference spectrum relating to the one of the first component and the second component.