PURPOSE: To control an EGR valve opening degree to a proper real EGR rate in relation to a demanded EGR rate by controlling an EGR valve opening degree suitably on the basis of a judging signal from a purge judging means.

CONSTITUTION: A rotational sensor 14 for detecting the number of engine revolutions and a load sensor 15 for detecting the load of an engine are provided as an engine operating condition detecting means. A means for detecting the control signal of a purge valve 10 is provided in a control unit 13 serving as a purge judging means. When it is judged by the control means in the control unit 13 on the basis of a detecting signal outputted from engine operating condition detecting means 14, 15 and a judging signal outputted from purge judging means 10, 13 that it is not in purge condition, an EGR valve opening degree is controlled to an exhaust reflux control (EGR) valve opening degree. On the other hand, when it is judged that it is in purge condition, the EGR valve opening degree is controlled to a degree reduced a prescribed value. It is thus possible to make an EGR rate correspond to a demand value so as to reduce HC and so on.