Opening timing of the intake valve of an internal combustion engine is controlled to take a value within a range from 30.degree. to 140.degree. after the top dead center of intake stroke during a period of time before completion of engine warming-up from starting of an engine, and also, effective opening area of the intake valve is made smaller than the effective opening area thereof that occurs after completion of engine warming-up in order to increase the flow velocity of intake air entering through the intake valve, and at the same time, fuel is injected into a combustion chamber during at least one of a first period of time in which the flow velocity of intake air is high immediately after the intake valve is opened and a second period of time previous to the first period of time in which the flow velocity of intake air is high, and during a third period of time starting immediately before ignition timing.