An injector drive circuit including: a step-up circuit generating a high voltage from a power supply; a first switching device connected to a path between the step-up circuit and an injector; a second switching device connected to the power supply; a third switching device connected between the injector and the ground; and a control unit operating the first, second and third switching device according to a value of current flowing through the injector; wherein the control unit has a unit turning on and off the second switching device in a period during which it turns on and off the first switching device a plurality of times; wherein the control unit has, as set values to control the current flowing through the injector, a first threshold defining a lower current limit, a second threshold defining an upper current limit and a third threshold, larger than the second threshold.