A control apparatus for an engine includes an engine, an EGR system, a spark plug, a controller, and a supercharging system. While a supercharging system is performing supercharging and the EGR system is introducing burned gas into a combustion chamber, in response to a control signal from the controller, the spark plug ignites air-fuel mixture at predetermined timing so that unburned air-fuel mixture combusts by autoignition after the air-fuel mixture starts to combust by the ignition.