The purporse of the present invention is to provide a circadian rhythm improving composition which can be safely taken over a long time, in particular, a circadian rhythm controlling composition capable of increasing circadian rhythm amplitude. Provided is a circadian rhythm improving composition comprising one or more kindes of lignan compounds.本發明係以提供一種可長期安全地攝取的晝夜節律改善用組成物,尤為一種可增大晝夜節律的振幅的晝夜節律調整用組成物為目的。解決手段為提供一種晝夜節律改善用組成物,其係包含1種以上之木聚糖類化合物。