An image forming apparatus includes an apparatus body, a holding member and a supporting member coupled to the holding member. The holding member includes photosensitive drums and is configured to hold toner cartridges disposed in association with the photosensitive drums in a detachable manner and to move between a storage position in which the holding member is accommodated in the apparatus body and a replacement position. The supporting member is configured to support light source arrays in association with the photosensitive drums, to cover the holding member, to move between a retaining position where the light source arrays are positioned relative to the photosensitive drums and a withdrawn position where the light source arrays are withdrawn from the photosensitive drums, and to move to the withdrawn position in a different direction than the direction in which the holding member is moved to the replacement position.