A developing roller composed of a rubber member including not less than two vulcanized rubber layers including a surface layer and a base layer. A hardness of the surface layer is set higher than that of the base layer. The hardness of the base layer is set to not more than 60 degrees in a JIS A hardness. A hardness of a laminate of all layers including the base layer and the surface layer is set to not more than 70 degrees in the JIS A hardness. An electric resistance value of the laminate is set to not more than 1010Ω, when the electric resistance value is measured by applying a voltage of 100V to the laminate at a temperature of 10° C. and a relative humidity of 20%.