A session identification unit (11) determines a session to which an incoming packet belongs, while a session relay unit (12-1-12-N) relays between a session with a transmission terminal and a session with a reception terminal. A packet scheduler (13) instructs and controls the delivery of packets from each session relay unit (12-1-12-N), and a delivery control unit (14) delivers packets from each session relay unit (12-1-12-N) based on the instruction. In the session relay unit (12-1), a transmission session processing unit (121-1) processes a session for transmitting data to the reception terminal, and a transmission buffer (122-1) stores received data until the end of a transmission. A reception session processing unit (123-1) processes a session for receiving data from the transmission terminal.