A four-stroke cycle in-cylinder fuel injection internal combustion engine (1) comprises a fuel injector (8) which injects fuel directly into a combustion chamber (7), performs stratified charge combustion by means of compression stroke fuel injection, and performs homogeneous combustion by means of intake stroke fuel injection. Upon start-up of the engine (1), intake stroke fuel injection is performed at the first combustion opportunity, and compression stroke fuel injection is switched to from the second combustion opportunity onward. In so doing, switching of the combustion system is performed early and independently of the engine rotation speed.