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 10.sup.10.OMEGA., when the electric resistance value is
measured by applying a voltage of 100V to the laminate at a temperature
of 10.degree. C. and a relative humidity of 20%.