An image forming apparatus includes: a light source that emits a laser beam; a polygon mirror that reflects the laser beam; a photoreceptor that is to be exposed to the laser beam reflected by the polygon mirror; a motor that rotates the polygon mirror; and a hardware processor capable of detecting sheet type, that is, type of a sheet conveyed in the image forming apparatus, wherein the hardware processor controls to rotate the motor at a first rotation speed until the sheet type is detected, and rotate the motor at a second rotation speed determined on the basis of the sheet type after detection of the sheet type.