Steps after a user finds an attractive product until he or she buys it are successively performed so that he or she can buy it stressfreely. The user photographs an attractive product with a portable camera telephone terminal 1 and transmits image data 7 to a server 3 through Internet 2. The server 3 has a DB 4 in which images such as various types of products, persons, and logo marks are registered and a DB 5 in which related information of image data registered in the DB 4 is registered. The server 3 performs an image recognizing process for the image data 7, retrieves data that match the image data 7 with a high match rate from the image data registered in the DB 4, and extracts corresponding related information from the DB 5. The related information is provided to the user through the Internet 2. By only transmitting the image data 7, the user can obtain related information of an attractive product. When the user accesses a site 6 for the product corresponding to the related information, he or she can obtain detailed information and buy the product.