Controller for internal combustion engine having fuel injection system

The invention relates to a controller (15) for an internal combustion engine (1) having a fuel injection system, which can realize an optimum injection even with a smaller inductance of a solenoid due to a smaller fuel injection valve (injector) and has a good property of minimum amount of fuel injection. A controller (15) for an internal combustion engine (1) having a fuel injection system with a solenoid comprising: a means for detecting an operating condition of the internal combustion engine; a means for calculating a fuel injection pulse width according to the above described detected operation condition; and a solenoid control means, wherein the above described solenoid control means includes, a means for supplying the above described solenoid a valve-opening current (40a) up to a large predetermined current value according to the above described calculated fuel injection pulse width; a means for supplying the solenoid a holding current for holding a valve opening state, after the above described valve-opening current (40a) has reached the predetermined current value; and a current waveform control means for forming a plurality of different current waveforms to be supplied to the above described solenoid and switching between the different current waveforms according to the above described detected operating condition.