There is provided a transmission rate control method. In this method, data is transmitted to a receiver at the most recent transmission rate RSNDt−1, and an RTCP packet including a reception rate RRCVt of the data is received from the receiver. When a network is in a congestion state, or when the network is in a non-congestion state and the most recent reception achievement rate RARt−1 is higher than the reception rate RRCVt, a reception achievement rate RARt is calculated as a long-term EWMA of the reception rate RRCV. When the network is in the non-congestion state and the most recent reception achievement rate RARt−1 is lower than the reception rate RRCVt, or when a time-out of the RTCP packet occurs, the reception achievement rate RARt is calculated as a short-term EWMA of the reception rate RRCV. A transmission rate RSNDt is set based on the reception achievement rate RARt.