The invention provides a method for improving sarcopenia of a subject in need thereof by using Phellinus linteus, in which the method includes administering an effective dose of composition to the subject, and the composition includes Phellinus linteus (NITE BP-03321 and BCRC 930210) as an effective substance. By using the aforementioned composition including an extract of a fermented product of the Phellinus linteus and/or its derivative, diameters of myotubes, amounts of muscles and muscle muscular endurance can be maintained, thereby improving sarcopenia.