To maintain physical fitness and health of middle-aged and older persons living in the threshold of the aging society, the present invention provides a fatigue reducing agent which is highly effective for preventing and reducing fatigue, wherein the agent is made of a composition of substances that are very safe so that long-term administration is possible. A composition containing reduced coenzyme Q was found to be effective for preventing and reducing fatigue, including muscle fatigue. Since the fatigue reducing effect of the composition of the present invention is seen not only in young rats but also more pronounced in aged rats, the present invention can provide the fatigue reducing agent which is very useful, especially, for middle-aged and older persons as well as for young people.