To provide a method and a device for multiplex transmission with which plural signals can be transmitted while being multiplexed under simple control at low cost.

At transmission equipment 50, an edge detector 52 detects the change of a data signal from H to L and outputs a synchronizing signal. After the lapse of every basic unit time (the inverse of bit rate), a transmission trigger outputter 53 outputs a transmission trigger and when the synchronizing signal is outputted before the lapse of the basic unit time, the measurement of the basic unit time is started again. Each time the transmission trigger is outputted, a transmitter 56 transmits the data signal and low-speed control signals 1-4 to a transmission line 60 while multiplexing them. A receiver 71 of reception equipment 70 detects the change of the signal received through the transmission line 60 from H to L and outputs a reception trigger. Each time the reception trigger is outputted, a level holder 73 and a 1:N selector 74 extract and hold the data signal and the low-speed control signals from the received signal.