At high temperature, namely, when the temperature of intake air is higher than a predetermined normal temperature range, an ECU (25) controls a variable valve timing mechanism (24) such that the timing for closing an exhaust valve (9) is adjusted to a retard side, thereby reducing the amount of high-temperature internal EGR gas to avoid the occurrence of pre-ignition. At intermediate load and high load, the ECU (25) makes the retard amount of the timing for closing the exhaust valve (9) larger than that at low load, thereby reducing the amount of internal EGR gas. At intermediate load and in an intermediate-revolution range or a high-revolution range, the rotating speed of an electric motor (16) is increased to raise a supercharging pressure exerted by a supercharger (17). At high load and in the high-revolution range, the electric motor (16) for the supercharger (17) and an EGR control valve (22) are controlled such that the supercharging pressure rises and the amount of external EGR gas increases as the temperature of intake air detected by a temperature sensor (26) rises.