System and Method of communication for navigation system, route guidance information transmitting device and terminal unit

A communication navigation system includes a server (SV) that transmits route guidance information to terminal units (T) via the Internet (IN), and a transmitter/receiver (15), provided in each terminal unit (T), for transmitting specification data that specifies a type of necessary route guidance information, to the server (SV) via the Internet (IN). The server (SV) transmits only the route guidance information of the type specified by the specification data, to the terminal unit (T).