An image forming apparatus according to an embodiment includes a photoconductive drum, a light scanning unit, a reflection mirror, a support member, and a cam. The light scanning unit forms a light scanning beam with which the photoconductive drum is irradiated. The reflection mirror guides the light scanning beam toward the photoconductive drum. The support member supports both ends of the reflection mirror in a longitudinal direction. The cam is provided in the support member. The cam comes into contact with the reflection mirror in an intermediate portion of the reflection mirror in the longitudinal direction. The cam moves the intermediate portion in a plate thickness direction of the reflection mirror with respect to a support position by the support member.