A fuel injection device includes a fuel injection valve for injecting fuel through a fuel injection orifice opening into a combustion chamber, an air injection valve for injecting air through an air injection orifice opening into the combustion chamber, sensors for detecting an operating condition of an engine, and an electronic control unit (ECU) for controlling the fuel injection valve and the air injection valve. Orientations of the air injection orifice and the fuel injection orifice are determined to make an air jet collide with a fuel spray. The ECU controls the fuel injection valve based on the operating condition detected by the sensors to control spray velocity, spray particle diameter, spray angle, etc. of the fuel to be injected through the fuel injection orifice, and at least one of an air injection timing and an air injection period of air injection to be performed by the air injection valve.