The present invention provides a service system using a certificate which is easily portable and difficult to counterfeit. The feature of the invention is to use a contactless IC chip as a portable certificate. An IC chip-attached seal is thin and small, and therefore is easily portable and distributable to a user. By integrating or attaching (or sticking) the IC chip into or on a certificate 3910, the counterfeiting of the certificate 3910 becomes difficult.