An engine (1) operates in a stratified charge combustion mode and a homogeneous charge combustion mode. A sensor detects driving state of the engine. An ECU (electronic control unit) (30) computes a basic amount of the fuel to be injected from a nozzle (11) based on the detected driving state of the engine. The ECU switches the combustion mode based on the computed basic amount. The ECU computes a corrected amount of the injection fuel based on the basic amount of the injection fuel. The corrected amount of the injection fuel suppresses a fluctuation of engine torque caused by switching of the combustion mode. The ECU controls the injection valve based on the computed corrected amount.