A cleaning unit includes a cabinet, a cleaning blade, a toner drop preventive sheet, and an auxiliary member. The cabinet has an opening facing an outer periphery of a photosensitive drum. The cleaning blade is operative to scrape down residual toner adhering to the outer periphery of the photosensitive drum. The toner drop preventive sheet is operative to prevent the residual toner scraped down by the cleaning blade from dropping between the photosensitive drum and the cabinet. The auxiliary member is disposed below the toner drop preventive sheet and is movable between a first position for receiving a bulk substance dropping from the toner drop preventive sheet and a second position for dropping the bulk substance received from the toner drop preventive sheet.