In a data delivery system utilizing a network 400, a data delivery server 100 receives a recording medium specifying information stored in a recording medium 300 from a video game device 200, generates and administers an authentication information and a password used to permit the delivery of an event information to the video game device 200 while relating them to the video game device 200, transmits the generated authentication information and password to the video game device 200, and delivers the event information to the video game device 200 upon receiving the password as a response from the video game device 200. The video game device 200 includes a password storage means for receiving the authentication information and the password from the data delivery server 100 and saving the password.