System for providing share of contents based on packet network in voice comunication based on circuit network

A system for servicing contents sharing during a voice call, a method, and a terminal for realizing the system are provided to perform a voice call using an existing PSTN(Public Switched Telephone Network) or CDMA(Code Division Multiple Access) network telephone number, while contents sharing between calling/called parties and mutual control for shared contents can be performed by using an IP(Internet Protocol) network. A registration server(210) maps IP addresses of subscriber terminals(100) given from the second communication network with telephone numbers of the terminals(100) given from the first communication network, and registers/manages the mapped information. A call server(220) takes charge of a call processing function for contents sharing requests received from the terminals(100). A contents sharing server(230) receives the requests from the call server(220) to set a data session for sharing contents by using the registered IP addresses between the subscriber terminal and the correspondent subscriber terminal which is in a voice call state, and controls a contents sharing function on the data session.