It is an object of the present invention to provide a reduced coenzyme Q, as a composition capable of being stably stored and, at the same time, soluble in water, which has not been used for industrial application because of its auto oxidation and lipophilic property. A reduced coenzyme Q-containing composition capable of being stored in a refrigerator or at room temperature for a prolonged period of time and of being soluble in water can be prepared by contacting or mixing the reduced coenzyme Q and a cyclodextrin to obtain a clathrated compound or by mixing an antioxidant, the reduced coenzyme Q and the cyclodextrin under an appropriate condition.
