To raise temperature of exhaust gas as required by raising exhaust gas temperature by throttling, only when it is has than a threshold.

An internal combustion engine 10 has an intake pipe 11 and exhaust gas conduit pipes 16, 18 that are open to an exhaust gas pipe. The intake pipe 11 is provided with a throttling device 24 that is equipped with an adjustable throttle valve. A connecting wire 42 is disposed between a control unit 30 and the internal combustion engine 10, to directly provide the internal combustion engine with information on valve opening to be selected or ignition timing adjustment. When temperature of an exhaust gas falls short of a predetermined threshold level, the control unit 30 sends a signal to the throttling device 24. This signal, which controls time and temperature, throttles air supply with the throttling device 24 and raises the exhaust gas temperature. Consequently, exhaust gas temperature control capable of bringing efficiency and exhaust to the best condition can be achieved.