1. An image forming apparatus which has an exposing portion adapted to expose an image bearing member, charged by a charging portion, based on image information, thereby forming an electrostatic latent image on the image bearing member, and a developing portion adapted to develop the electrostatic latent image formed by the exposing portion by a toner, thereby forming a visible image, and in which transfer material, on which the visible image formed by the developing portion has been transferred, is conveyed to a fixing portion, and the visible image is fixed onto the transfer material by the fixing portion, comprising: an extracting portion adapted to extract lateral line image information of a lateral line image extending in a main scanning direction from the image information; a control portion adapted to control a light emission amount of the exposing portion, so as to control an amount of the toner which is developed based on the lateral line image information in order to prevent a scattering of the toner associated with the evaporation of moisture contained in the transfer material at the time when the lateral line image is fixed by the fixing portion; and an obtaining portion adapted to obtain material kind information representing a kind of transfer material on which the lateral line image is fixed by the fixing portion, wherein the control portion changes the control of the light emission amount for preventing the scattering according to the material kind information.