A developing device includes a developer transport path through which a developer is agitated and transported, a developing roller mounted in the developer transport path, a discharging unit extending from the developer transport path in a length direction of the developing roller, the discharging unit including an air outlet from which air is discharged and a developer discharge outlet from which the developer is discharged, and a separating member mounted in the discharging unit to separate an inner portion of the discharging unit into an air discharge path, connecting the developer transport path and the air outlet, and a developer discharge path, connecting the developer transport path and the developer discharge outlet.