Abstract: A mass spectrometry method by a liquid chromatograph-mass spectrometer that can detect an organic acid with high sensitivity by retaining, separating and eluting the organic acid without adding any nonvolatile substance to a mobile phase and without receiving any restriction of a ratio of a water-soluble organic solvent, and an analytical column are provided. The mass spectrometry method is a mass spectrometry method for an organic acid by a liquid chromatograph-mass spectrometer, wherein a column packed with a hydrophilic polymer having an anion-exchange group is used, and as a mobile phase, a water-soluble organic solvent-water mixed solution is used. The analytical column is a column for liquid chromatography for an organic acid, in which a polyether ether ketone (PEEK) resin housing for liquid chromatography is packed with a hydrophilic polymer having an anion-exchange group.