There are provided a developing unit and a developer stirring and transporting method in which the amount of developer in the developing unit can always be kept at a specified amount without being influenced by a use environment. A developing unit 10 includes a developing roller 12, a containing unit 16 to contain the developer and having a discharge port 14 to discharge the overflown developer in its side wall, a stirring and transporting member 20 to stir and transport the developer along a passage 18 formed in the containing unit 16, and a guide unit 22 provided in the passage 18 correspondingly to the discharge port 14 of the containing unit 16 and to guide the developer transported in the passage 18 by the stirring and transporting member 20 to the discharge port 14 side.