The present invention relates to a prophylactic antistress agent and a central fatigue improver, which contain chlorogenic acids or pharmaceutically acceptable salts thereof as active ingredients. The present invention makes it possible to prevent and improve mental task fatigue, physical fatigue, central fatigue, central fatigue syndrome, overwork and the like.本發明係關於將漂木酸類或其藥學上可接受之鹽作為有效成分之預防性抗壓力劑及中樞性疲勞改善劑。藉由本發明,可預防和改善腦力活動引起之疲勞、肉體疲勞、中樞性疲勞、中樞性疲勞症候群、過勞等。