PURPOSE: To provide the residue developer detection device where the precision of residue quantity of the developer is stable and an accurate judgement that the residue quantity of the developer has reached the specified residue quantity can be carried out.

CONSTITUTION: The residue developer detection device is provided with an image forming cartridge 20 where the toner can be contained, light emitting element 100 irradiating light from outside of this image forming cartridge 20 to the inside of the hopper 63, a light receiving element 101 receiving the light which was irradiated inside the hopper 63 outside the image forming cartridge 20 and outputting signal according to the received light and a control means MC judging whether or not the residue quantity of the toner inside the hopper 63 has become the specified residue quantity based on the signal from the light receiving element 101. The judgement is made by the control means MC that the residue toner quantity has become the specified residue quantity, especially when a state where light trasmission detection time T when the signal from the light receiving element 101 is exceeding the threshold value V2 set beforehand is generated more than five times during a second specified period which is longer than the first specified period.