In an image forming apparatus of a type wherein toner is replenished to a developing unit by turning or rotating a toner bottle, a phenomenon that a toner replenishment amount per turn of the bottle (replenishing rate) is decreased as the toner remaining quantity in the bottle is decreased, is utilized to provide a method and an apparatus for easily and reliably determining a toner near empty state when a number of the turns measured by counting a number of detection of an object to be sensed formed on an outer surface of the toner bottle.