To provide an image forming apparatus that suppresses deterioration of toner, while maintaining detection accuracy of the remaining amount of toner.

In a state where the rotation period of an agitator 31, which is associated with detection of the remaining amount state of toner, is set to a predetermined short period, if the detected remaining amount state of toner in a developing cartridge 24 is determined not to be in a "full state," the rotation period of the agitator 31, which is associated with detection of the remaining amount state of toner, is set to a long period.