A sialylated glycan analysis method using mass spectrometry for analyzing a structure of a sialylated glycan to which a sialic acid is linked, the method comprising: a) a modification step in which a linkage-type-specific modification is performed on a sialic acid residue included in a sialylated glycan to be analyzed; b) an analysis execution step in which the sialylated glycan after the modification by the modification step is subjected to a mass spectrometric analysis to obtain mass spectrum information; c) a candidate estimation step in which a candidate of a monosaccharide composition is estimated for a peak observed on the mass spectrum obtained in the analysis execution step, based on mass information of the peak; and d) a candidate-narrowing step in which a plurality of peaks observed on the mass spectrum and having a mass difference corresponding to a technique of the linkage-type-specific modification are assumed to be a cluster of peaks corresponding to sialylated glycans including sialic acid residues of a same kind with different linkage types and being identical in the monosaccharide composition exclusive of the sialic acid residues, and monosaccharide composition candidates obtained for those peaks are narrowed down by judging each monosaccharide composition candidate from at least one of following aspects: (i) excluding a monosaccharide composition candidate which does not include a sialic acid residue; (ii) excluding a monosaccharide composition candidate which does not include a specific type of modified sialic acid residue; (iii) excluding a monosaccharide composition candidate which does not include a predetermined number of a specific type of modified sialic acid residue; (iv) excluding a monosaccharide composition candidate which is not identical in a monosaccharide composition exclusive of the sialic acid residue. a) a modification step in which a linkage-type-specific modification is performed on a sialic acid residue included in a sialylated glycan to be analyzed; b) an analysis execution step in which the sialylated glycan after the modification by the modification step is subjected to a mass spectrometric analysis to obtain mass spectrum information; c) a candidate estimation step in which a candidate of a monosaccharide composition is estimated for a peak observed on the mass spectrum obtained in the analysis execution step, based on mass information of the peak; and d) a candidate-narrowing step in which a plurality of peaks observed on the mass spectrum and having a mass difference corresponding to a technique of the linkage-type-specific modification are assumed to be a cluster of peaks corresponding to sialylated glycans including sialic acid residues of a same kind with different linkage types and being identical in the monosaccharide composition exclusive of the sialic acid residues, and monosaccharide composition candidates obtained for those peaks are narrowed down by judging each monosaccharide composition candidate from at least one of following aspects: (i) excluding a monosaccharide composition candidate which does not include a sialic acid residue; (ii) excluding a monosaccharide composition candidate which does not include a specific type of modified sialic acid residue; (iii) excluding a monosaccharide composition candidate which does not include a predetermined number of a specific type of modified sialic acid residue; (iv) excluding a monosaccharide composition candidate which is not identical in a monosaccharide composition exclusive of the sialic acid residue. (i) excluding a monosaccharide composition candidate which does not include a sialic acid residue; (ii) excluding a monosaccharide composition candidate which does not include a specific type of modified sialic acid residue; (iii) excluding a monosaccharide composition candidate which does not include a predetermined number of a specific type of modified sialic acid residue; (iv) excluding a monosaccharide composition candidate which is not identical in a monosaccharide composition exclusive of the sialic acid residue.