PURPOSE: To effectively attain improvement of engine performance and suppress excessive consumption of fuel by accurately adjusting an air-fuel ratio of air-fuel mixture to be supplied to a cylinder based on detection of property of exhaust by means of an exhaust sensor.

CONSTITUTION: An exhaust sensor 91 is arranged for detecting property of exhaust 100 generated by combustion inside a cylinder. An air-fuel ratio of air-fuel mixture intaken in the cylinder is adjusted based on the detection signal of the exhaust sensor 91. A guide passage 115 is formed for guiding the exhaust 100 outside a system, while an accumulator chamber 119 communicated with the guide passage 115 is formed. The property of the exhaust 100 in the accumulator chamber 119 is detected by the exhaust sensor 91. A throttle 131 is provided on one division end 122 of the guide passage 115 to the accumulator chamber 119.