An image forming apparatus is provided. The image forming apparatus includes: a photosensitive member; a discharging unit arranged to face the photosensitive member; a high-voltage power supply unit which supplies power to the discharging unit; a discharge detection unit which detects abnormal discharge in the discharging unit; an output controller which controls an output of the high-voltage power supply unit according to control information; and a cleaning detection unit which compares current control information for the high-voltage power supply unit supplying power to the discharging unit in which abnormal discharge is detected with previous control information for the high-voltage power supply unit when previous abnormal discharge is detected in the discharging unit, and which detects whether the discharging unit has been cleaned based on the comparison result.