A developing device comprising: 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 comprising an air outlet from which the air is discharged and a developer discharge outlet from which the developer is discharged; and a separating member mounted in the discharging unit and configured 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, wherein the developer transport path comprises a developing chamber extending in a length direction of the developing roller and including the developing roller, an agitating chamber disposed in parallel to the developing chamber, and a barrier wall configured to divide the developing chamber and the agitating chamber and comprising at both ends of the barrier wall first and second flue holes (231, 232) that communicatively connect the developing chamber and the agitating chamber, wherein a first agitating member transporting the developer to the developer discharge outlet is mounted in the developing chamber, characterized in that the discharging unit extends from the developing chamber, wherein the first agitating member extends into an inner portion of the developer discharge path, and wherein the separating member elastically contacts the first agitating member. 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 comprising an air outlet from which the air is discharged and a developer discharge outlet from which the developer is discharged; and a separating member mounted in the discharging unit and configured 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, wherein the developer transport path comprises a developing chamber extending in a length direction of the developing roller and including the developing roller, an agitating chamber disposed in parallel to the developing chamber, and a barrier wall configured to divide the developing chamber and the agitating chamber and comprising at both ends of the barrier wall first and second flue holes (231, 232) that communicatively connect the developing chamber and the agitating chamber, wherein a first agitating member transporting the developer to the developer discharge outlet is mounted in the developing chamber, characterized in that the discharging unit extends from the developing chamber, wherein the first agitating member extends into an inner portion of the developer discharge path, and wherein the separating member elastically contacts the first agitating member.