An image forming apparatus includes: a photosensitive member; a scorotron charger; a developing device; a voltage application circuit; a constant-voltage circuit; a first control device; a deboost circuit; and a second control device, wherein the deboost circuit has a circuit configuration in which a resistor and a control transistor are connected in series with each other, and deboosts the grid voltage by a voltage drop of the resistor to generate the developing voltage, and the second control device provides a control signal to the control transistor to control a current flowing in the resistor, thereby controlling the level of the developing voltage.