Abstract: To realize various additional service functions, which are available in a main device of a conventional button telephone system, in a voice over IP telephone. [Solving Means] A voice over IP telephone apparatus for carrying out voice communication adapted to an Internet Protocol (IP) through Internet is made to include a transmission/additional information generating and analyzing unit 12 for generating, at a transmitting side, additional information of service content to be added to transmission information related to a transmitter and a receiver as a destination, and for analyzing, at a receiving side, the additional information added to the transmission information transmitted by the transmitter to obtain the service content.