A technique is provided that can reduce degradation of the sound quality due to a tandem connection of paired coding and decoding, and can reduce the operation processing amount and the required memory amount of a multipoint control unit. At a terminal of a communication network having a larger communication capacity in multipoint connection between terminals in a plurality of communication networks (e.g., a fixed phone line and a mobile phone line) having different communication capacities, a multichannel coding including a monaural coding scheme of the communication network having the smaller communication capacity is performed on the coding side, whereas decoding of a multichannel-coded code of one point, decoding of a monaural-coded code of one point, or decoding of a monaural-coded code of a plurality of points is performed on the decoding side in accordance with the input code.