An image forming apparatus at least includes a photoreceptor, a light emitter, a detector and a controller. The light emitter irradiates the photoreceptor with a laser beam so as to form an electrostatic latent image thereon. The detector detects an incident amount of the laser beam falling on a light receiving portion of the detector on a main scan line. The controller changes at least one of a detection sensitivity of the detector for a laser beam and an emission amount of the laser beam emitted from the light emitter when the incident amount of the laser beam detected by the detector is not greater than a predetermined value.