Provided is a composition for preventing or treating insomnia. The composition includes, as an active ingredient, extract of Phlomis umbrosa Turcz. or a combination thereof with extract of Polygala tenuifolia Willd. Particularly, the combination of extract of Phlomis umbrosa Turcz. with extract of Polygala tenuifolia Willd. enables recovery of the sleep of patients suffering from insomnia nearly to that of normal persons. The composition for treating insomnia uses active ingredients that have been used as Chinese traditional medicines, and thus is safe to the human body.