A developing device includes a developer vessel, a flow-path forming portion, and an exhaust duct. The developer vessel accommodates developer composed of toner and carrier. The flow-path forming portion includes a plurality of connection flow paths. The exhaust duct has an intake port communicating with the plurality of connection flow paths, and a filter that covers the intake port is disposed at the intake port of the exhaust duct. Each of the plurality of connection flow paths has an inlet communicating with an internal space of the developer vessel, an outlet communicating with an internal space of the exhaust duct, and a cross-sectional area increasing 5 to 20 times from the inlet toward the outlet.