A developing roller includes a roller main body disposed to face, without contact, an outer circumferential surface of an image carrier. The roller main body includes a resin coat layer that is formed on an outer circumferential surface of a base body that is made of a metal including aluminum, the resin coat layer being made of a resin material and having electric conductivity. An AC impedance Z obtained from an application of an AC voltage at a frequency in a range from 0.05 Hz to 100 Hz is equal to or higher than 100Ω, and a phase angle θ satisfies a relationship of 0 rad