an image forming apparatus includes an image bearing member carrying an image corresponding to image information ; an image transfer device for transferring the image on the image bearing member onto a transfer material at a transfer position , wherein the transfer device includes a charging member contactable to a back side of the transfer material and voltage application means for applying a voltage to the charging member , wherein the voltage applying device effects a constant voltage control to the charging member when an image region of the image bearing member is at the transfer position , and effects a constant current control to the charging member at least a part of the other duration , and wherein a voltage level of the constant voltage control is determined on the basis of a voltage across the transfer device during the constant current control ; wherein voltage applied to the charging member by the voltage applying device or a current through the charging member by the voltage applying device is limited .