An image forming apparatus comprises: a storage medium 35 configured to arrange in a toner cartridge 30; a detection sensor 37 configured to detect the toner specific concentration of the developer in the developing apparatus 14; a control unit 100 configured to calculate a value corresponding to the drive time of the drive motor 31 to calculate an integrated count value for the toner cartridge, and output a message containing the cause of an abnormity corresponding to the count value when the toner specific concentration detected by the detection sensor shows a value indicative of the empty of the toner, wherein the count value and an empty information indicating whether or not the toner cartridge is empty are stored in the storage medium.