A skin information processing method for a skin information processing device that includes a storage portion includes include acquiring an image, and determining a base point that represents a sweat pore on a ridge of skin, from the acquired image and acquiring position information corresponding to a position of the base point on the image. The skin information processing method includes acquiring sample information indicating changes in color information around the determined base point, generating, as frequency information, information associating frequency components of the acquired sample information with the position information. The skin information processing method includes causing the storage portion to store information including the generated frequency information and the position information of the base point, as information used in skin authentication.