A control/monitor signal transmission system in which simple communication control can be performed without a control unit, and a wiring allowable distance is larger than a conventional system. A plurality of slave stations which are installed corresponding to the plurality of actuating apparatuses and are connected through a common data signal line, and a mediation station which is connected to the data signal line are equipped, and the data signal line includes a plurality of independent groups which are consolidated to the mediation station. The plurality of actuating apparatuses are divided into one or plural sets including at least two, and the actuating apparatuses which belong to the same set and are different in group of the connected data signal line have a correspondence relationship. The mediation station extracts monitor data from a monitor signal transmitted from the sensor unit through the slave station, and transmits the monitor data as control data to a different actuating apparatus which has a correspondence relationship with the actuating apparatus including the sensor unit which transmits the monitor data.