An image forming apparatus including an image bearing member and a developing device configured to develop an electrostatic image on the image bearing member with a toner to form a toner image thereon and including a developing unit configured to develop the electrostatic image, and a toner cartridge configured to supply the toner to the developing unit through at least one opening, wherein the developing device circulates the toner between the toner cartridge and the developing unit through the at least one opening, and wherein the internal temperature of the hopper is higher than that of the cartridge and the ratio of a charge quantity distribution parameter of the toner under a condition of 45.degree. C. and 54% RH to that under a condition of 25.degree. C. and 54% RH is greater than 0.9 and less than 1.5.