A developing device includes a developer container that accommodates an electrostatic image developer including toner containing a toner particle and a zinc stearate particle, a ratio (DT/DS) of a volume-average particle size (DT) of the toner particle to a volume-average particle size (DS) of the zinc stearate particle being about 1.9 or more; a developer carrier that supplies the toner to an image carrier; a supply conveyor that supplies the electrostatic image developer while conveying the electrostatic image developer; a mixing conveyor that conveys the electrostatic image developer while mixing the electrostatic image developer; and a partition disposed between the supply conveyor and the mixing conveyor. The electrostatic image developer is moved from the supply conveyor to the mixing conveyor through a first passage and is moved from the mixing conveyor to the supply conveyor through a second passage.