The present invention relates to a process for purifying dimeric to pentameric proanthocyanidin oligomers which comprises extracting the proanthocyanidin oligomers from raw materials containing the proanthocyanidin oligomers or crude purification products therefrom by solid-liquid extraction using methyl acetate as a liquid phase; a process for purifying dimeric to pentameric proanthocyanidin oligomers which comprises pretreating with an enzyme for hydrolysis raw materials containing the proanthocyanidin oligomers, crude purification products therefrom, or a solution containing one of these; and a process for purifying dimeric to pentameric proanthocyanidin oligomers with a uniform polymerization degree which comprises separating and purifying the proanthocyanidin oligomers by polymerization degree from raw materials containing the proanthocyanidin oligomers or crude purification products therefrom by normal phase silica gel liquid chromatography using as a mobile phase a single solvent or a mixed solvent of two or more solvents selected from the group consisting of an ester solvent, a ketone solvent, a hydrocarbon solvent, an ether solvent and an alcohol solvent.