To prevent the occurrence of leak with an image carrier or adhesion of a carrier to the image carrier and sufficiently supply toner to an electrostatic latent image in the development of the electrostatic image formed on the image carrier by carrying a developer containing the toner and carrier to a developing area where a developer carrier is opposed to the image carrier, and working an electric field to the developing area.

In this developing device for carrying a developer containing toner and a carrier held on the surface of a developer carrier 11 to a developing area where the developer carrier 11 is opposed to an image carrier 1 and working an electric field between the developer carrier and the image carrier to supply the toner to an electrostatic latent image formed on the image carrier, the impedance per unit area Zs (Ω/cm2) on the surface of the developer carrier and the impedance Zc (Ω.cm2) in the carrier satisfy the condition of 1.8×105≤Zs.Zc≤2.1×109.