An image forming apparatus (1, 1, 1") includes multiple image forming units (20Y, 20C, 20M) disposed adjacent to and horizontally aligned with each other, a first transfer member (15) to sequentially transfer and overlay respective single non-black color images thereon, a black image forming unit (20K, 20K', 20K") disposed separately from the multiple image forming units (20Y, 20C, 20M) including a black image carrier (2K) and a black image developing unit (4K, 4K'), a second transfer member (12) to transfer the black image from the black image forming unit (20K, 20K', 20K") onto a recording medium, a first cleaning unit (5K) to clean the black image carrier (2K), and a second cleaning unit (13) to clean the second transfer member (12). The black toner removed from the surface of the black image carrier (2K) is collected to the black image developing unit (4K, 4K').