To enable each information terminal 22 to easily implement IP phone.

An IP phone server 21 stores an IP phone module 26, by which each information terminal implements IP phone, and routing information 28 for each information terminal in a database 24 and determines a routing path to a speech destination information terminal in accordance with stored routing information 28 in response to a connection request from each information terminal 22 and performs IP phone exchange between a speech source information terminal and the speech destination information terminal. Each information terminal 22 is provided with hardware 38, which is used to implement IP phone of a voice input/output device and a GUI device, and an IF program 50 which operates hardware, and each information terminal sends a transmission request of the IP phone module 26 to the IP phone server through the Internet 1 and stores and holds the received IP phone module and uses this stored IP phone module, hardware, and the IF program to implement IP phone.