A developing device includes a housing having an opening in a wall thereof, a developing roller rotatably arranged within the housing, and a magnetic pole structure, wherein the developing roller is configured to carry a developer on an outer surface thereof using the magnetic force of the magnetic pole structure. The developing device further includes a gap forming member located within, and spaced from, the housing at a location downstream, in the rotation direction of the developing roller, of the opening in the wall of the housing, forming a first gap with respect to the developing roller and forming a second gap with respect to the housing, a blocking member arranged in the first gap, and a guide section configured to guide airflow passing through the second gap in a general direction toward the developing roller.