In-vehicle network control system

A main controller (100) as a master apparatus and respective actuator units (MIX, MODE, F/R) as slave devices carry out serial data communication through a LIN bus (BUS), and when it is detected that a battery power source voltage is out of a predetermined voltage (for example, 7.3-18 volts) by battery power source monitoring means (130) of the main controller (100), transmission of communication data is stopped by communication permitting means (111).