PURPOSE: To effectively suppress a fuel consumption amount and a discharge amount of HC by performing one cycle of combustion in a given high load area during a time in which a crankshaft performs one full turn and performing one cycle of combustion in a given low load area during a time in which the crankshaft performs a plurality of full turns.
CONSTITUTION: During running of an engine, an electronic control device ECU 6 inputs a signal G indicating that a piston 14 of a first cylinder is positioned at a top dead center, a signal N indicating that the pistons 14 of first - third cylinders are respectively positioned at a top dead point, and an intake air pressure signal (b), and outputs a fuel injection signal (a) to a fuel injection valve 4 of the first cylinder when the signal G is inputted. An engine load is decided by means of an intake air pressure signal (b), and in a given high load area, the injection signal (a) is orderly outputted to fuel injection valves 4 of the second and third cylinders when the signal N is inputted. Meanwhile, in a low load area, after the signal G is inputted, the injection signal (a) is outputted to the fuel injection valve 4 when the signal N is inputted two times. When the signal N is inputted further two times starting from a fuel injection timing, the signal (a) is outputted to the fuel injection valve 4 of the second cylinder.