A method is disclosed which sets a PoC Box service and transmits information on a service identifier by using a standard SIP, a SDP, an XCAP, and a PAP, in order to remain compatible with conventional PoC technology when performing call processing of session connection using a PoC Box. Further, the method stores only pre-designated media in a PoC Box according to a type of media transmitted in consideration of features of a PoC multimedia session.