In the present invention, advertisements are transmitted electronically at designated locations, as a substitute for stationary billboards. A network navigation center outputs guide access information GAI to a personal computer of an ad sponsor over the Internet and receives registration of advertisement information ADI for the designated location(s) from the personal computer of the ad sponsor according to the guide access information GAI. In addition, the network navigation center receives current position information API from mobile communication device(s) carried by automobile, via a mobile telephone base station and a public telephone network. Likewise, the network navigation center transmits the advertisement information ADI, based on current position information API, to the mobile communication instrument via the public telephone network and mobile telephone base station.