By means of preventing counterfeits on the market from entering a distribution channel, the benefit of manufacturers, dealers, distributors, and consumers forming the distribution channel. First, a data server reads ID data of a non-contact tag 11 and of a reader 12, creates data files thereof, and stores the data files in a database. The reader 12 connected to the Internet reads its own ID data and sends it to an authentication server. The authentication server checks the received ID data of the reader 12 against the data file of the reader 12 stored in the database. If the two are identical, the reader is authenticated. The authenticated reader 12 reads the ID data of the non-contact tag 11 embedded in a product and sends it to the authentication server. The authentication server checks the received ID data of the non-contact tag 11 against the data file of the non-contact tag stored in the database. If, as a result, the two are identical, the authentication server notifies the reader 12 that the non-contact tag is authenticated. The product authentication system is administered and operated by an application service provider (ASP) entity 10.