To restrain generation of knock and keep operation feeling and exhaust gas performance well without increasing fuel injection amount excessively, by providing a detecting means for detecting knock state of an engine and changing at least fuel injection timing when knock is detected.

A setting means 205 sets a fundamental fuel injection amount based on output signals from a rotation speed detecting means 202 and a load detecting means 203. An air-fuel ratio detecting means 201 detects air-fuel ratio oxygen concentration) after combustion, an air-fuel ratio control means 206, based on the detection signals, calculates fuel injection amount so that the air-fuel ratio equals to theoretical air-fuel ratio, and a fuel injection valve 13 is controlled. An engine operation state judging means 207, based on output from the load detecting means 203, judges whether an engine is in a normal state or in an acceleration state. When a knock state detecting means 204 detects knock state of any cylinder, a knock preventing means 208 corrects fuel injection timing according to the judged engine operation state.