To provide a technology capable of realizing high-accuracy detection of toner density.A developing apparatus includes: a partition plate provided within the developing apparatus for partitioning an interior of the developing apparatus into a plurality of space; plural transport mixers each provided in the space within the developing apparatus partitioned by the partition plate and rotating for stirring and transporting a developer including toner and carrier; a density sensor provided in a transport path of the developer in one space of the plurality of space partitioned by the partition plate for detecting toner density of the stirred and transported developer; and retracting part for retracting an amount of the developer more than a predetermined amount into another space than the space in which the toner density is detected by the density sensor so that the amount of developer is constantly equal to or less than the predetermined amount near a toner density detection position by the density sensor.