A light scanning device which exposes a photoconductor of an image forming apparatus, includes: a light emitting unit which emits a light; a mirror which reflects a light emitted by the light emitting unit in a direction toward the photoconductor; an obtaining unit which obtains data on a speed of an image formation; and a mirror support unit which has at least one contact member provided so that it can be brought into contact with or be detached from the mirror, and which changes at least one of a position and a number of contact members contacting the mirror on the basis of data obtained by the obtaining unit.