An object of the present invention is to provide an analgesic effective in a prophylactic or a therapy for various pain diseases. The present invention is to provide an analgesic containing an ester of C10 fatty acid as an active ingredient. The analgesic of the present invention containing the compound as an active ingredient is highly useful as a prophylactic or therapeutic agent for various pain diseases such as the pain caused by osteoarthritis (e.g., knee osteoarthritis and hip osteoarthritis) or by demyelinating diseases such as multiple sclerosis or Guillain-Bareé syndrome.
