An image forming apparatus has a light scanning apparatus which is capable of aligning a lens with a plurality of light-emitting devices and forming a high-quality image while suppressing generation of moiré. In a first image formation mode, light-emitting devices outputting light beams exposing both ends of the photosensitive member in a rotational direction and at least a part of light-emitting devices exposing an area between exposure positions of the light-emitting devices outputting the light beams exposing the both ends are used to form an electrostatic latent image on the photosensitive member. In a second image formation mode, the light-emitting devices outputting the light beams exposing both ends are not used, and at least a part of light-emitting devices exposing an area between exposure positions of the light-emitting devices outputting the light beams exposing both ends are used to form the electrostatic latent image on the photosensitive member.