1. An image forming apparatus, comprising: a developing unit which develops an electrostatic latent image formed on an image carrier, using toner; a toner storing unit in which toner fed from a toner supply unit is stored; a conveying unit which conveys toner from the toner storing unit to the developing unit; a toner-in-toner-storing-unit detecting unit which detects a state of toner in the toner storing unit; a toner-in-developing-unit detecting unit which detects a state of toner in the developing unit; and a determining unit which determines a state of toner in the toner supply unit based on a detection result of the toner-in-toner-storing unit detecting unit, with the determining unit not determining the state of toner in the toner supply unit when the toner-in-developing-unit detecting unit detects a predetermined amount of toner.