The present invention provides a stabilization method of reduced coenzyme Q 10 useful as food, food with nutrient function claims, food for specified health uses, nutritional supplement, nutritional supplement, animal drugs, drinks, feeds, cosmetics, pharmaceutical products, therapeutic drugs, prophylactic drugs and the like, as well as a stabilized composition. Furthermore, it provides a convenient production method of reduced coenzyme Q 10 using oxidized coenzyme Q 10 as a starting material. In the present invention, oxidation of reduced coenzyme Q 10 can be suppressed, and reduced coenzyme Q 10 can be stably maintained by the co-presence of a licorice hydrophobic extract and reduced coenzyme Q 10 . In addition, reduced coenzyme Q 10 can be produced by the co-presence of oxidized coenzyme Q 10 and a licorice hydrophobic extract.
