The image forming apparatus, to which a developing apparatus for developing a latent image on an image bearing member corresponding to image information is detachably attachable, includes, a first detection device for detecting an amount of developer in the developing apparatus; a second detection device for detecting a utilized amount of the developer in the developing apparatus based upon the image information, and a processing unit for judging a utilized amount level of the developing apparatus based upon results of detection of the first detection device and the second detection device, wherein the processing unit judges the utilized amount level of the developing apparatus using the result of detection of the first detection device and the result of detection of the second detection device until the result of detection of the first detection device reaches a predetermined value, and judges the utilized amount level of the developing apparatus using the result of detection of the first detection device after the result of detection of the first detection device has reached the predetermined value. Consequently, it becomes possible to detect the residual amount of developer with high accuracy.