An image forming apparatus comprises an exposure department for exposing photographic paper conveyed at a first conveying speed, a development department for developing the photographic paper, conveyed at a second conveying speed lower than the first conveying speed, after being exposed in the exposure department. In the image forming apparatus, the relationship between 1) the distance along the conveying direction from a reference area to a micro area being the target of exposure correction, both the reference area and the micro area being on the photographic paper, and 2) the difference in tone between images formed at the reference area and the micro area when the reference area and the micro area are exposed to the same amount of light in the exposure department, and the relationship between the exposure of the photographic paper and the tone of the image at the reference area are stored.