A developing unit according to an embodiment of the present disclosure includes a developer container, a stirring member, a magnetic roller, a developing roller, a developer supply port, and a developer discharge portion. The developer discharge portion includes a discharge blade having a spiral blade and conveying an excess developer, a developer discharge port through which the excess developer conveyed by the discharge blade is discharged outside of the developer container, and an air outlet through which an airflow in the developer container passes toward the outside of the developer container. The developer discharge port is located at a position lower than the upper surface of the developer present in the developer discharge portion; and the air outlet is located at a position higher than the upper surface of the developer present in the developer discharge portion.