A transfer-source terminal, a communication-destination terminal, and a nearby terminal existing in the neighborhood of transfer-source terminal are provided. The nearby terminal collects connectivity information for monitoring connectivity after terminal switching by performing a communication process with the communication-destination terminal, and transmits the connectivity information collected to the transfer-source terminal. The transfer-source terminal receives connectivity information from the nearby terminal by a connectivity information receiving unit, determines a transfer-destination terminal from among the nearby terminals according to connectivity information by a transfer-destination terminal determinating unit, and transfers a communication session with a communication-destination terminal to the transfer-destination terminal determined, by a session transferring unit.