PURPOSE: To improve the electrostatic chargeability and release property of a toner and to prevent the generation of after-images at the time of long-term repetitive use by using conductive particles which are more negative in electrostatic chargeability than a resin constituting an electrode layer when a positive charge toner is used and using the conductive particles which are more positive in electrostatic chargeability than the above-mentioned resin when a negative charge toner is used.

CONSTITUTION: A developing roller 5 has the electrode layer 21 contg. at least the resin and the conductive particles 23 in the outermost layer. The conductive particles 23 are made more negative in electrostatic chargeability than the resin constituting the layer 21 when the positive charge toner 2 is used. The particles are made more positive in electrostatic chargeability than the resin constituting the layer 21 when the negative charge toner 2 is used. For example, metallic particles of Ni, Cu, etc., having the higher negative electrostatic chargeability than fluoroplastic are used as the conductive particles 23 when the positive charge toner is used as the toner if the constituting resin of the electrode layer 21 is the fluoroplastic. Metallic particles of Al, Zn, Fe, etc., having the higher positive electrostatic chargeability than the fluoroplastic is used when the negative charge toner is used as the toner. The electrostatic chargeability and release property of the toner are improved and the generation of the after-images at the time of long-term repetitive use is prevented.