An image forming apparatus and a control method thereof are provided that determine a final contrast potential taking into consideration not only the relationship between the contrast potential of an electrostatic latent image and the density value of a developed image but also a toner charge amount for developing the electrostatic latent image. To accomplish this, the image forming apparatus of the present invention predicts, in advance, the contrast potential of the electrostatic latent image and the density of the toner image at the contrast potential for a predetermined toner charge amount. Furthermore, the image forming apparatus forms an image by adjusting the relationship between the contrast potential and density measured in advance based on a current toner charge amount and a saturation toner charge amount when forming the image.