PROBLEM TO BE SOLVED: To provide more effective skin-lightening methods or skin-lightening agents, and further provide more efficient and simpler methods of evaluating the skin-lightening effects of test substances.SOLUTION: More effective skin-lightening methods or skin-lightening agents are achieved by the activation of Langerhans cells of the skin. Methods of evaluating the skin-lightening effects of test substances use the activation of Langerhans cells of the skin as indices.