To perform precise control of the fuel amount under the disturbance by which fuel pressure is changed, by detecting fuel pressure to be applied to an injector, taking the ratio of the detected fuel pressure to reference fuel pressure, and correcting the fuel injection pulse length.

A starting time reference pulse length table is a table of the engine cooling water temperature, retrieves and outputs the starting time reference pulse length Tis by taking the water temperature as an input. In the transition of fuel pressure rising, the starting time reference pulse length Tis is multiplied by the fuel pressure correction factor and corrected, and fuel injection is performed. That is, the injection pulse length from an injector 9 is changed according to the width of the actual fuel pressure. First, fuel pressure is read by a fuel pressure sensor 23 of an engine 7, the water temperature is read, and table retrieving of the starting time reference pulse length is performed. The fuel pressure ratio is found from reference fuel pressure and the measured fuel pressure, retrieving of the fuel pressure correction factor FPhos is performed, and the injection pulse length Ti is found from the expression of Ti=Tis×FPhos+Ts. The letter Ts indicates the invalid pulse length.