To develop a novel glycomics tool that can enable anyone to identify oligosaccharides very easily and quickly, we have recently constructed a library of observed multistage tandem mass (MS(n)) spectra for oligosaccharides. However, this approach requires the preparation of a large variety of structurally defined oligosaccharides. Therefore, simulation of the tandem mass spectrum for any given structure would be another powerful approach with which to improve the above method. By performing collision-induced dissociation (CID) experiments of sets of oligosaccharides complementarily labeled with (13)C(6)-D-galactose, we identified characteristic fragment patterns for each branch type of N-linked oligosaccharides. On the basis of these characteristic fragment patterns, we could simulate CID spectra for three isomeric oligosaccharides. In addition, we successfully demonstrated the identification of an oligosaccharide by matching its CID spectrum against the library of simulated tandem mass spectra. This strategy will be a useful tool for glycomics, as well as for approaches based on the library of observed MS(n) spectra.