Provided is a technique for decomposing a resveratrol glycoside, preferably decomposing a resveratrol glycoside and an isoflavone glycoside, and thus promoting aglycone production to thereby increase the absorbability thereof into a living body. A bacterium belonging to the genus Bifidobacterium is used as an active ingredient of an aglycone production promoter that is to be used for promoting the production of an aglycone from glycoside(s). The aglycone production promoter is used in a medicinal composition for preventing and/or treating diseases on which aglycone exerts an effective action or a food or drink composition for producing an aglycone.
