An object is to provide a sleep quality improving agent that can sufficiently exert the effect of improving the quality of sleep and ensures safety for the body. A sleep quality improving agent containing, as an effective ingredient, a plant of the Fraxinus genus such as Fraxinus excelsior L., an extract thereof, Larix sibirica extract, dihydroquercetin, dihydrokaempferol, or naringenin, and a sleep quality improving composition containing the sleep quality improving agent are provided.
