To provide the multiplex transmission method in which not fixed channel arrangement but dynamic channel arrangement is attained and management of a flexible channel and band is facilitated.

In the multiplex transmission method, a modulation channel is configured to be a multi-frame of a fixed length, the multi-frame consists of single frames each having a fixed length, and one single frame 203 is made up of a synchronizing signal 208, a multiplex channel number 209 and transmission data 210. A server discriminates to which multiplex channel an AV stream to be sent is assigned according to a request from a terminal equipment and the decided channel number is stored in a channel number 209 and the resulting frame is sent. After demodulating the modulation channel, the terminal equipment separates the single frame 203 designated by the channel number by the server precedingly in terms of a multiplex frame from the multi-frame 201, decodes the transmission data 210 and provides an output of video/audio signals.