An image forming apparatus includes: a main body; a photosensitive drum rotatably supported in the main body; a developing unit detachably accommodated in the main body in a direction along an axis of the photosensitive drum in a state where the photosensitive drum is disposed in the main body. The developing unit includes: a developer carrying member configured to carry developer for supplying the developer to the photosensitive drum; a developing frame supporting the developer carrying member; and a supporting assembly configured to support the developing frame such that, in a state where the developing unit is accommodated in the main body, the developing frame is movable between a proximity position where the developer carrying member and the photosensitive drum being positioned adjacent to or in contact with each other and a separation position where the developer carrying member and the photosensitive drum being separated from each other.