PURPOSE: To prevent the occurrence of white smoke or the like in time of running at highland, by compensating a fundamental exhaust recirculation flow rate to be determined according to engine load for reduction in proportion to a drop in suction pressure when the engine load is below the specified value, while controlling the exhaust circulation with the recirculation flow rate after being compensated.

CONSTITUTION: In time of engine operation, at a control unit 25, first a fact of whether or not it is in time of idling is discriminated, and when 'YES' is the case, a compensation coefficient K is determined according to suction pressure Pm detected by a suction pressure sensor 30, causing it to be stored in memory. On the other hand, when 'NO' is the case, a fundamental duty ratio D is determined on the basis of each output out of an engine speed sensor 26 and a fuel injection quantity sensor 29 and after that, a fact of whether or not it is in time of high load driving is discriminated, and in case of 'NO', the fundamental duty ratio D is given to a suction pressure control valve 43 as it is as an output duty ratio Do . On the other hand, when 'YES' is the case, the output duty ratio Do being found by adding up the compensation coefficient K to the fundamental duty ratio D is given to the suction pressure control valve 43, and with control of the said valve 43, the opening of an exhaust gas circulation control valve 34 is controlled.