To provide liquid chromatograph mass spectrometry and its device for analyzing sensitively mass spectrometry of a sample containing peptide or protein, and further performing its sequence analysis.

The sample containing the peptide and/or the protein is injected into a separation column filled with separation base material having one or more functional groups selected from the group comprising the hydroxy group, an amido group and the carboxyl group. The peptide and/or the protein are, then, separated by normal phase liquid chromatography using eluant prepared by adding acid to mixed liquid of organic solvent and water and/or alcohol, and then, provided for a mass spectrometer.