There is provided an image forming apparatus and method capable of reducing a measurement error in a measurement result of the surface potential of an electrostatic latent image formed on the surface of an image bearing member. The measurement error occurs under the influence of an electric field generated from a pre-exposed area. Consequently, miniaturization of an image forming apparatus and consistent print quality can be achieved. The image forming apparatus includes an image forming control section for determining an error correction value corresponding to the charge state of a latent image on the basis of relationships between charge states of the latent image and error correction values which have been prepared in advance, computing an error corrected potential measurement value using the error correction value and a potential measurement value, and controlling the image forming apparatus on the basis of the error corrected potential measurement value.