A temperature sensor detects information regarding humidity in an atmosphere of a developing container. A temperature sensor detects information regarding humidity in an atmosphere of a toner hopper. An inductance sensor detects information regarding a toner density within the developing container. A printer controller controls a replenishing operation of a replenishing screw member based on image information. The printer controller controls the replenishing operation of the replenishing screw member so that a toner density within the developing container is less than or equal to a predetermined value based on a detection result of the inductance sensor. The printer controller controls the predetermined value to be small when a difference between humidity detection results detected by each of the temperature sensors is large as compared to when the difference is small.