Anti-fatigue agents containing dioxabicyclo[3.3.0]octane derivatives such as sesamin which is an ingredient contained in sesame, as well as pharmaceutical compositions and physiologically functional foods that contain such anti-fatigue agents are disclosed. These compounds can safely be administered to humans and animals alike and hence allow for continued ingestion while proving effective in promoting an improvement of stamina, an increase of body strength, a relief of fatigue, and recovery from fatigue.