An image forming apparatus including an image bearing member (1); a charge member (2) contacted to the image bearing member to electrically charge the image bearing member; voltage applying means (20,21) for applying to the charge member an oscillating voltage including an AC voltage component; first detecting means (26) for detecting an AC current applied to the charge member from the voltage applying means; second detecting means (23) for detecting the AC current corresponding to a peak or a neighborhood of the peak of the AC voltage; control means for effecting control such that current detected by the second detecting means is a predetermined level when the current detected by the first detecting means is within a predetermined range and such that current detected by the first detecting means is a predetermined level when the current detected by the first detecting means is outside the predetermined range.