Controlling apparatus and method of internal combustion engine

A target homogeneous mode throttle opening TA1 that is suitable for homogeneous stoichiometric combustion without EGR is computed regardless of the current combustion mode. During homogeneous stoichiometric combustion without EGR, the opening of a throttle valve (23) is controlled based on the target homogeneous mode throttle opening TA1. During homogeneous stoichiometric combustion with EGR, an opening adjustment value TAo is added to the target homogeneous mode throttle opening TA1 and the resultant is set as a target EGR throttle opening TA2. The opening of the throttle valve (23) is controlled based on the target EGR throttle opening TA2. During stratified lean combustion, the fuel injection amount is controlled based on a hypothetical throttle opening TA1, which corresponds to the target homogeneous mode throttle opening TA1. In either combustion mode, the engine torque is adjusted based on a common control value, which is the target homogeneous mode throttle opening TA1. Therefore, the engine torque is not abruptly changed when the combustion mode is switched.