PURPOSE: To effectively reduce NOx at initial acceleration and to improve accelerating condition later on by conducting negative pressure through an atmospheric air conducting valve into a negative pressure chamber of a flow control valve of an exhaust recirculating device and mixing air in the negative pressure chamber at the latter part of the acceleration.

CONSTITUTION: Intake and exhaust manifolds 2, 3 of an engine 1 are connected by an exhaust recirculating passage 4 with the first and the second flow control valves 6, 7. Suction negative pressure is conducted into a negative pressure chamber 62 of the first valve 6 through a pressure-regulating valve 30 where exhaust gas pressure is regulated. Into a negative chamber 72 of the second valve 7, suction negative pressure in the downstream of a throttle valve 21 is conducted, and an atmospheric air conducting valve 9 is provided in a negative pressure passage 8. Said valve 9 has two diaphragms 92, 95, and negative pressure in the direct upstream and downstream of the throttle valve 21 is conducted into negative pressure chambers 91, 94. Being thus constituted, the conducting valve 9 stays still at the inital acceleration, and air is conducted into the passage 8 in the latter period of the acceleration.