PURPOSE: To enlarge the stable combustion limit region of an engine by drivingly controlling a heating device on the basis of the result of detection in an intake temperature sensor so that intake temperature may attain a preset value.

CONSTITUTION: A lean-burn internal combustion engine has a lean-burn operation domain in which combustion is executed in a lean state where an actual air-fuel ratio is larger than a theoretical one, and is provided with an exhaust recirculating device (EGR) to partially return exhaust gas into intake gas. A lean-burn engine 10 is provided with a heating device to heat intake air, and the temperature of the intake air supplied into a combustion chamber 18 is detected by an intake temperature sensor 35. In addition, a drive-control means drivingly controls the heating device on the basis of the result of detection in the intake temperature sensor 35 so that the temperature of the intake air may attain its preset value. Thus the stable combustion limit region of an engine can be improved to widen the domain of possible operation for facilitating the operation in a lean high EGR domain.