In a communication system having at least three communication devices communicating with each other, a seating-order determination device for generating seating-order information for information sent from each communication device and for transmitting the seating-order information to each communication device is provided. Each communication device controls the output position of each information according to the seating-order information to output the information sent from the other communication devices in a seating order corresponding to the seating-order information. The seating order is always automatically changed to the most appropriate condition according to the progress of a conference and the state of conversations to provide the user with a comfortable conference environment and a comfortable communication environment.