A search for copyright-related information contained in image data is conducted. If no such information is detected, a database is queried to determine whether it contains copyright-related information corresponding to the image represented by this image data. Information relating to a copyright in accordance with the result of querying the database is added onto the image data. This prevents the unauthorized copying of a copyrighted article in an environment in which digitized copyrighted articles can be exchanged by networking and electronic filing.