A developing roller including a semiconductive rubber member having not less than two vulcanized layers including a base layer composed of a vulcanized electro-conductive rubber composition and a surface layer composed of a vulcanized rubber composition. An electric resistance value of the base layer is set to not more than 10.sup.7.OMEGA., when the electric resistance value of the base layer is measured by applying a voltage of 100V thereto at a temperature of 10.degree. C. and a relative humidity of 20%. An electric resistance value of a laminate of all layers including the base layer and the surface layer is set not more than 10.sup.7.OMEGA. in the same condition as the above-described condition in which the electric resistance value of the base layer is measured.