To provide an image forming apparatus in which an optical write device inside and optical elements inside the optical write device are hardly affected by heat caused by external factors.

A 1st guide part 50C is arranged oppositely to the surface of an area moving from a side Y to a side X on polygon mirrors 62a and 62b, and a 2nd guide part 50D is arranged at an opposed position to the 1st guide part 50C in a state where the mirrors 62a and 62b are put in between. In the case of rotating the mirrors 62a and 62b, a part of an air current going toward the side Y from the side X goes toward a side wall 50b on the side Y by the 2nd guide part 50D, and a part of an air current going toward the side X from the side Y is guided by the circular-arc shaped guide surface of the 1st guide part 50C so as to join with the air current going toward the side Y from the side X.

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