In an image forming apparatus in which toner is fed to a developer unit (6) from a toner storage container (32) through toner conveying means (40) provided between the toner storage container (32) and the developer unit (6), the image forming apparatus comprises a toner remaining amount detector (101) for detecting an amount which is not higher than a predetermined amount of toner in the toner storage container (32), a toner density detector (102) for detecting the density of toner in the developer unit (6), and means (110) for interrupting the image forming operation to feed the toner to the developer unit (6) from the toner storage container (32) through the toner conveying means (40) when the amount of the toner in the toner storage container (32) is larger than the predetermined amount and the density detected by the toner density detector (102) is lower than a predetermined density. Consequently, suitable measures can be taken when there occurs such a state that no toner is present in the toner conveying means (40) between the toner storage container (32) and the developing mechanism even if there is toner in the toner storage container (32).