An image forming apparatus includes an image bearing member having a
photosensitive surface and an optical writing apparatus generating a
laser beam modulated according to image data. The optical writing
apparatus includes a housing, an optical deflector, an f-theta lens and a
separator. The optical deflector is configured to rotate to deflect the
laser beam. The f-theta lens is configured to correct the laser beam
deflected by the optical deflector and to transmit a corrected laser beam
towards the image bearing member. The separator is configured to separate
an inside space of the housing into at least two sections including a
first section in which the optical deflector is mounted and a second
section in which the f-theta lens is mounted. The separator includes a
heat resistant transparent plate disposed at a position of crossing
passage of the laser beam between the optical deflector and the f-theta
lens.