An image forming apparatus including: a photosensitive member rotatable in a first direction; an exposure unit configured to scan the photosensitive member with a light beam in a second direction substantially orthogonal to the first direction to form a latent image; a generation unit configured to generate data corresponding to a gradation of a predetermined pixel of input image data by dividing the predetermined pixel by a predetermined division number; a calculation unit configured to calculate an ideal division number depending on a position of the predetermined pixel in the second direction; and a determination unit configured to determine the predetermined division number based on the ideal division number, wherein the determination unit feeds back an error between an ideal division number and a division number for a pixel at a position preceding the predetermined pixel in determining the predetermined division number for the predetermined pixel.