An image forming device is provided with an image carrier and a transfer material adsorber and conveyor. The conveyor is provided for attaching a transfer material by an electrostatic force and for conveying in a first direction the transfer material to a position in which the image carrier is brought into contact at a transfer site. The conveyor comprises an electrical field generator for generating an electrical field downstream of the contact point with respect to the first direction. The electrical field generator is arranged on a side opposite to a surface in contact with the transfer material on the conveyor. The electrical field generator comprises a contact-type electricity feeder. An insulating layer is provided having a volume resistivity of at least 10.sup.14 .OMEGA.cm arranged on the side of the surface in contact with the image carrier, and a high resistance layer is further provided having a volume resistivity of between 10.sup.8 to 10.sup.14 .OMEGA.cm. A surface potential of the side in contact with the transfer material resulting from the electrical field generator has a potential gradient having a peak proximate to a position downstream of the contact point with respect to the first direction.