An object of the present invention is to provide a new muscle atrophy inhibitor comprising a component that is safely ingestible for a long time. It was found that glycosides of quercetin, a polyphenol present in plants, etc., have inhibitory activity on the expression of myostatin involved in muscle atrophy. This invention provides a new muscle atrophy inhibitor comprising a quercetin glycoside which is excellent in absorbability into the body and high in safety.
