Abstract: A transferring device for transferring on a record paper a toner image formed onto an image forming member is disclosed. The transferring device comprises a transfer belt with a dielectric layer formed on a conduction belt member; a driving device for running the transfer belt; a transfer roller for contacting the transfer belt to an image forming member with pressure; a corona charges arranged at a position opposite to the transfer belt for charging the transfer belt with a charge having a polarity opposite to the charging polarity of the toner; a grid electrode arranged between the corona charger and the transfer belt; a plurality of bias sources connected to the grid electrode for biassing the grid electrode at respective potentials; and a change-over circuit for changing over the connection between the grid electrode and the bias source, whereby the grid potentials are selectively changed over in accordance with the characteristics of a record paper to be used.