An image forming apparatus includes a main body, exposing portions each forming a latent image on a photosensitive drum based on image data by driving of a polygon motor, developing portions each developing the latent image formed on each of the exposing portions using toner, and a partition member provided between each of the exposing portions and each of the developing portions. Projecting portions each including the polygon motor project from the partition member toward a side of the developing portion. Each of the projection portions is overlapped with at least a part of each of the developing portions on a vertical direction. The cooled air flows to the overlap portion in which the polygon motor of each of the exposing portions and each of the developing portions are overlapped.