To allow each user performing communication to check his/her communication partner based on reliable information independent from operation of a call control terminal, when third person call control is executed using a (3PCC) system.

Upon receipt of an INVITE signal directing call a connection of user terminals UA1 and UA2 from a call control terminal UA3, a SIP (Session Initiation Protocol) server verifies whether or not a call origination has been made as described in information on third person call control (third person call control header) inserted into a header of each INVITE signal. When it is determined that the call origination has been made as described in the information on third person call control as the result of the verification, the SIP server inserts warranty information into the header of the INVITE signal, and relays it to the UA1 and the UA2 to be connected respectively to notify that the call originated is a signal which connects the terminals (between UA1-UA2) by third person call control employing the UA3 as the starting point.