An image forming apparatus includes an optical system unit and an attachment board. The optical system unit forms an electrostatic latent image by irradiating an image bearing member with light. The optical system unit is attached to the attachment board. The attachment board includes a mounting surface, a first recess portion, and a second recess portion. The optical system unit is mounted on the mounting surface. The first recess portion and the second recess portion are provided in the mounting surface to form air paths. The first recess portion is located below a lower surface of the optical system unit, extending in a first direction. The second recess portion is located below the lower surface of the optical system unit, extending in a direction different from the first direction and crossing the first recess portion.