PURPOSE: To suppress a torque variation while preventing the increase of NOx, without using an air-fuel scope generating NOx, by opening and closing a solenoid valve so as to control to convert a three-way change-over valve, in order to feed either a bypass air or an EGR gas to a suction passage, according to the air-fuel ratio of a mixture.

CONSTITUTION: A bypass passage 26 to bypass a throttle valve 22 in the suction passage 18 of an internal combustion engine 2 is provided, and a three-way change-over valve 28 is provided on the way of the bypass passage 26. And an EGR passage 30 whose one end is connected to an exhaust gas passage 20 is connected to the three-way change-over valve 28, and a connecting passage 34 to connect the diaphragm chamber 32 of the three-way change-over valve 28 and the suction passage 18 is also provided. A solenoid valve 36 is provided to the connecting passage 34, and it is operated controlled by a controller 38, so as to control to convert the three-way change-over valve 28. By such a way, either the air from the bypass passage 26, or an EGR gas is fed to the suction passage 18, according to the air-fuel ratio of the mixture. Consequently, an air-fuel ratio scope generating NOx is never used.