When a plurality of toner containers mounted on a developing rotary unit are simultaneously determined as toner-absent toner containers, toner container replacement may not be efficient because toner containers are replaced at a replacement position. Therefore, when the toner containers mounted on the developing rotary unit are simultaneously determined as toner-absent toner containers, a toner container to be preferentially replaced is selected so as to be able to be placed at a replacement position by considering the usability of the toner containers.