An image forming apparatus includes: a developing unit for developing a latent image on an image bearing member by using a developer containing toner and a carrier; and a detecting unit for detecting a density of a detection reference toner image, wherein detection results obtained by the detecting unit are employed to control a toner replenishment operation for the developing unit, and wherein, when the detection results obtained by the detecting unit is equal to or smaller than a predetermined value, a residual toner amount determination mode is performed. The residual toner amount determination mode includes: a toner replenishment step of performing an operation for replenishing toner; a detecting step of performing the detecting unit to detect the density of the detection reference toner image; and a comparison step of comparing a first detection result obtained at the detection step with a second detection result obtained by the detecting unit before said toner replenishment step is performed the first time, and for which respective performance of the steps is enabled while an image forming operation is halted, and wherein, based on the results obtained at said comparison step, whether the residual toner amount determination mode should be continued is determined.