In an image forming apparatus in which positioned below a development unit for accommodating a toner is an exposure unit that writes to a photosensitive drum by exposing an electrostatic latent image, an aperture portion on an upper surface of an exposure unit case positioned in an optical path of light from the exposure unit is provided so as to not become an impediment to the optical path of the light and a glass plate is inclined and provided on the aperture portion. An inclination angle of the glass plate is set to an angle inclined 40° with respect to a horizontal line so as to be greater than a repose angle of the toner when the toner has poor fluidity under a condition of high temperature and high humidity.