The invention provides a developing apparatus capable of measuring the concentration of carbon dioxide absorbed by a developing solution which exhibits alkalinity and managing the concentration of carbon dioxide absorbed by the developing solution which exhibits alkalinity. The developing apparatus includes a developing solution preparing device that mixes a developing stock solution containing amain component of the developing solution that exhibits alkalinity with pure water to prepare a developing solution having a predetermined concentration as a developing new liquid; a developing new solution pipeline for conveying the developing new liquid supplied from the developing solution preparing device to the repeatedly used developing solution; and a developing stock solution pipeline forconveying the developing stock solution to the repeatedly used developing solution; a pure water pipeline for conveying pure water supplied to the repeatedly used developing solution; and a developingsolution management device for managing the repeatedly used developing solution to a predetermined component concentration or a specified concentration range.