An image forming apparatus includes an image bearing member, an exposure unit, and a main housing. An electrostatic latent image is formed on the image bearing member. The exposure unit includes an optical device that irradiates the image bearing member with light to form the electrostatic latent image, and a housing that defines a storage space in which the optical device is located. The main housing includes a partition wall that divides an inner space of the main housing into a first space in which the image bearing member is located and a second space in which the exposure unit is located. The housing includes a first opening wall having a first opening through which the storage space communicates with the second space. The optical device irradiates the image bearing member with light through the first opening.