In a conveyance path made up of guide plates which guide a copy sheet to a transfer region between a photoreceptor and an opposing transfer device and a second guide plate for conveying the copy sheet to a fixing rollers, the guide plates and the fixing rollers including a pre-fixing guide, which all will be in contact with copy sheets, are grounded via a common resistor having a high resistance. An adjuster resistor is interposed in series between the common resistor and the guide plates positioned before transfer which are closer from the transfer region compared to the fixing rollers. When a copy sheet resides across the transfer region with both sides in contact with the guide plates and fixing rollers or with one side in contact, the total current that flows during a transfer operation is practically determined by the common resistor which has a high resistance. Accordingly, the flowing current can be limited within a certain range, thus it is possible to stabilize the transfer potential and hence to achieve a stabilized transfer operation.