A switch instruction is transmitted from a PC terminal (105) to a portable PC terminal (107) (S302); the portable PC terminal (107) transmits a switch connection request to a portable communication terminal (102) on the other end of communication (S306); the portable PC terminal (107), when it is waiting for a response to the switch connection request and receives a switch connection request from the other end of communication, detects that switching processes are being performed simultaneously (S312); upon detection of the simultaneous switching, a switching session related to either switch connection request is determined to be continued (S314 and S315); the portable PC terminal (107), which received the switch connection request to which the switching session determined to be continued was related, transmits a success response including information on the switching process of the portable PC terminal (107) side (S316 and S319); and the PC terminal 101, which received the switch connection request to which the one to be stopped was related, transmits a failure response (S317 and S318). This allows switching to be carried out with quick and not many procedures in both end communication terminals performing multimedia communication with each other.