Abstract: The present disclosure relates to a composition for skin improvement and a pharmaceutical composition for preventing or treating an inflammatory skin disease, the compositions including an umbilical cord-derived mesenchymal stem cell culture medium as an active ingredient. The compositions exhibit a wound relief, wrinkle improvement, regeneration, elasticity increase, moisturizing, barrier strengthening, anti-inflammatory or antioxidant effect, and thus can be effectively used as a cosmetic composition for skin improvement or a pharmaceutical composition for preventing or treating an inflammatory skin disease.