An image forming apparatus includes a body casing, a plurality of process cartridges, and a moving member. Each process cartridge includes a photosensitive drum having a rotation axis extending in a first direction. The plurality of process cartridges are configured to move between an engaging position and a release position in a second direction perpendicular to the first direction. The photosensitive drum and the positioning member engage with each other in the engaging position, and are disengaged from each other releasing the engagement in the release position. The moving member in a pressing position is configured to exert pressure so that the process cartridges are moved to the engaging position. The moving member in the non-pressing position is configured to release the pressure so that the process cartridges are moved to the release position.