An image forming apparatus includes a pressure unit and first and second positioning portions. A photosensitive unit, configured to be mounted in a main frame of the image forming apparatus along a prescribed direction, may include a plurality of photosensitive drums, a pair of metal plates, and a resin frame. The pair of metal plates is spaced away from each other in the axial direction of each photosensitive drum and supports the photosensitive drums. The metal plates are configured to be positioned on the second positioning portion. The resin frame is configured to support the metal plates and developer cartridges. The resin frame is further configured to be positioned on the first positioning portion. The pair of metal plates is pressed against the second positioning portion to be positioned with respect to the main frame when the resin frame is pressed by the pressure unit in the prescribed direction.