An image forming apparatus for and a method of compensating for development mass per area includes a photosensitive body on which an electrostatic latent image for an image is formed, a charger charging the photosensitive body, a developing unit developing the electrostatic latent image of the photosensitive body, a measuring unit measuring a charge current flowing through the photosensitive body from the charger, a comparator comparing the charge current with a reference current, and a controller controlling a developing unit control variable so as to compensate for a variation in a thickness of the photosensitive body according to an output of the comparator. A time indicator of a display informs a user whether the photosensitive body has to be replaced, and deterioration of an image quality caused by a decrease in the thickness of the photosensitive body can be prevented when a potential of the developing unit is controlled.