A developing device comprising: a developer vessel that accommodates a developer containing a toner and a carrier; a toner supply port; a developing roller; a developer conveying passage; a developer conveying helical member; and a developer scooping member, wherein the developer conveying passage includes a first developer conveying passage and the a second developer conveying passage being defined by a partitioning plate, and a first communicating path and a second communicating path that establish a communication between the first and second developer conveying passage, the developer conveying helical member includes a first developer conveying helical member disposed in the first developer conveying passage, and a second developer conveying helical member disposed in the second developer conveying passage, the developer scooping member includes a first developer scooping member disposed near the first communicating path to send the developer in the first developer conveying passage into the second developer conveying passage, and a second developer scooping member disposed near the second communicating path to send the developer in the second developer conveying passage into the first developer conveying passage.