A sensor control device is connected with a plurality of exhaust sensors including an NOx sensor to be disposed around a catalyst, and is constructed such that a plurality of drive control circuits to be connected in a one-to-one relationship with the individual gas sensors are disposed in one casing. The sensor control device is provided with a communication output section that outputs signals through a digital communication line so that the signal transmissions/receptions with an ECU may be executed through the digital communication line. This digital communication line is physically a one-system cable but can transmit and receive signals of a plurality of kinds with predetermined communication protocols.