An image forming apparatus includes a detected-current-controlled voltage charging device for charging a transfer material before a toner image is transferred to the transfer material by a transfer device. A current is produced when a voltage is applied to the charger device before the toner image is transferred. The voltage applied to the transferring device when the image-formed portion of the transferring material passes a transferring part is controlled on the basis of a current produced by a predetermined voltage applied to the transfer device when a leading edge portion of the transferring material passes the transferring part, and the predetermined voltage is controlled on the basis of the output from the current detector.