An image forming apparatus includes an image bearing member; a charging member contactable to said image bearing member for effecting contact charging of said image bearing member, said charging member being capable of being supplied with a voltage having a DC component and an AC component, and said charging member being provided with an electrode for receiving the voltage; wherein the following is sataisfied: when an electric field formed between said image bearing member and said electrode is not more than |E/d SD |[V/m], a resistance of said charging member per unit area of contact between said image bearing member and said charging member is larger than 20E/(wCV DC )[Ωm 2 ]    and is larger than the resistance when the electric field is more than |E/d SD |[V/m], and not more than |(E+V DC )/d SD |[V/m]
   where E[V] is an amplitude of the AC component; w[rad] is an angular velocity of t AC component; d SD [m] is a minimum distance between said electrode and said image bearing member; C[F/m 2 ] is an electrostatic capacity per unit area of said image beating member; and V DC [V] is a voltage of the DC component.