A transmission device for rigorously protecting important information when information is transferred via a best-effort network. In this transmission device, a quality control information retention unit holds quality control information set by a user. A delay amount instruction unit determines the retransmission upper limit frequency of packets for each real-time streaming on the basis of transmission quality information from a reception device and the quality control information held by means of the quality control information retention unit. Retransmission control units accumulate packets during a fixed period in accordance with the retransmission upper limit frequency determined by means of the delay amount instruction unit, and generate retransmission packets in accordance with a retransmission request from the reception device.