A multicast transmission system includes a server and a plurality of terminal devices, the servers and the terminal devices connected through a network. Each terminal device includes data transmission means for transmitting data to the server during a PTT call, and output means for receiving counting result data from the server and outputting the counting result data. The server includes counting means for counting or tallying up data received from the terminal devices, and counting data transmission means for transmitting the counting result data to the terminal devices used by members of the PTT call.