An image forming apparatus includes an image bearing member for bearing a developer image; a developing device including a developer carrying member for forming the developer image on the image bearing member; a fixing device for fixing the developer image on a sheet material, on which the developer image has been transferred, by heating the sheet material; a memory medium for storing an operation hysteresis value, of the developing device, which varies depending on a state of an operation of the developing device from start of the operation; and a controller for controlling a temperature of the fixing device. The controller controls, when the operation hysteresis value stored in the memory medium reaches a preset threshold, the temperature of the fixing device so as to be lower than that before the operation hysteresis value reaches the preset threshold.