An image forming apparatus includes an image forming unit including an image bearing member, and a casing on which a discharge port is formed, the casing including a first frame, a second frame disposed below the first frame in a vertical direction, a side cover, and a top cover, the first frame including a side plate that supports an end, in a longitudinal direction, of the image bearing member. At least one of the top cover and the first frame includes a first pillar portion. The second frame includes a second pillar portion. The side cover includes a third pillar portion disposed between the first pillar portion and the second pillar portion in the vertical direction, the third pillar portion being provided at a position at least partially overlapping with the first pillar portion and the second pillar portion when viewed in the vertical direction.