According to an embodiment of the invention, a sliding plate that slides in contact with an inner wall of a disposed toner duct is oscillated by using rotation of a disposed toner collection auger. As the sliding plate is oscillated, disposed toner falling and fed through the disposed toner duct is oscillated. The disposed toner adhering to the inner wall of the disposed toner duct is removed by sliding of both lateral parts of the sliding plate in contact with the inner wall.