Image forming equipment having a developing device for developing a latent image electrostatically formed on an image carrier by a developer, and a cleaning device for removing the developer remaining on the image carrier and collecting it in a collecting section. The equipment determines whether or not the developer collected in the collecting section has reached a predetermined amount by determining whether or not a developer has been supplemented to the developing device a predetermined number of times. The number of times that a developer is supplemented to the developing device is counted on the basis of the output of a supplement detector which determines whether or not a developer has been supplemented. The supplement detector determines that developer has been supplied only when a predetermined number of copies have been made after a toner low/empty signal is indicated or the toner concentration is detected to increase after the toner low/empty signal is indicated.