An image forming apparatus including an electrostatic image forming device, which forms an electrostatic image on an image bearing member, a developing apparatus, which develops the electrostatic image by a development bias being applied to a developer carrying member carrying a developer, a distance changing device, which changes the closest distance between the image bearing member and the developer carrying member, a density detecting portion, which detects the density of a developer image for detection formed by the developing apparatus, and a controller operable to execute a developer lifetime detecting mode for detecting the developer image for detection formed with the closest distance changed by the distance changing device, by the density detecting portion, and informing information regarding the lifetime of the developer based on the result of this detection.