In a multicast distribution system in which terminal devices on a distribution path are hierarchically grouped, a first terminal device which has detected a loss of a receiving packet transmits to a second terminal device located upstream of the first terminal device a retransmission request for a packet retransmission to the first terminal device and a third terminal device which receives a packet first in a group located downstream of a group to which the first terminal device belongs. The second terminal device which has received the retransmission request transmits a retransmission packet to both the first and third terminal devices.