An image forming apparatus includes a rotatable image bearing member; an exposure unit, disposed below the image bearing member, including a transmitting portion for transmitting a laser beam to which the image bearing member is exposed; a developing unit disposed above the exposure unit for developing, with toner, a electrostatic latent image formed on the image bearing member; and a toner supply opening for supplying toner into the developing unit above the exposure unit, wherein the toner supply opening is in a range, with respect to a rotation axial direction of image bearing member, inside an end of the exposure unit and outside the transmission portion.