To solve a problem that change of key information is impossible due to a lack of time for changing the key information between one antenna and one road side radiocommunication installation, since a communication area is for a narrow radiocommunication system when the key information stored in a vehicle-mounted unit is to be changed to new key information using radiocommunication.

A plurality of the antenna and the road side radiocommunication equipment are installed along non-exit sections of a toll road so as to provide a longer communication time. Authentication and information processing period are combined to be in sequence in chronological order as partners of communication even when communication sections are intermittent, whereby the key information stored in the vehicle-mounted unit can be changed.