The present invention pertains to: the provision of a method for promoting skin wound healing and a composition to be used for promoting skin wound healing; the provision of a method useful for preventing or ameliorating ulcers and bedsores or a composition therefor; the provision of a method for preventing skin aging and a composition to be used for preventing skin aging; the provision of a composition useful for preventing or ameliorating skin damage caused by an anticancer agent; and, furthermore, the provision of a method for enhancing the regeneration ability of epidermal stem cells and a composition for enhancing the regeneration ability of epidermal stem cells. More specifically, use of a composition, said composition being characterized by comprising, as an active ingredient, a substance selected from the group consisting of a substance which induces or maintains the expression of COL17A1 in cells, a substance which inhibits the degradation of COL17A1 in cells, a substance which promotes the competitive amplification ability of epidermal stem cells, a substance which suppresses genomic stress or oxidative stress in cells and a substance which prevents DNA damage in cells, enables the promotion of skin wound healing, protection from an anticancer agent and prevention of skin aging. Thus, the regeneration ability of epidermal stem cells can be enhanced.