A communication conference system that enables users who have only a connecting unit via a telephone line network and users who have only an IP connecting unit to hold a talk session mutually without a need of an expensive dedicated conference server is provided. A talk session device 1 includes a network processing portion for transmitting/receiving voice information to/from other equipments via IP, and a terminal for inputting/outputting a voice signal. The talk session device 1 is connected to a handset terminal of a telephone 3 via an adaptor 2 that converts the standards (mainly a level) of the voice signal. The talk session device 1 is connected to other talk session devices via IP, and is connected to other telephones by a telephone line via the telephone 3. Accordingly, a user serving as a destination of the IP and a user serving as a destination of the telephone line are connected mutually.