For changing services to readers who desires to obtain electronic books exactly or minutely, an electronic book management system 1 distributes at least electronic purchase certificates relating to books which are stocked at a bookstores owing a bookstore terminal device 2, in advance, to that bookstore terminal device 2. When buying the book(s), a reader obtains in an IC card 4 owned by her/him a purchase certificate(s) of that book(s) which she/he bought, from the bookstore terminal 2. When ordering to obtain the electronic book(s), the reader transmits the purchase certificate(s) from a reader terminal device 3 to the electronic book management system 1 through a communication network 5. The electronic book management system 1 changes over it's service when supplying the electronic book(s) to that reader depending upon the existence of the purchase certificate(s).