IMAGE FORMING APPARATUS

An image forming apparatus having: an image carrier being rotatable while carrying a toner image; a transfer member being rotatable while forming a transfer nip by being pressed by the image carrier, the image carrier being made with an ion conductive material; a power supply continuously applying a transfer bias voltage to the transfer member as a plurality of print media pass through the transfer nip, the transfer bias voltage having a predetermined polarity; and a control section determining whether the resistance of a nip-margin area has exceeded a predetermined resistance threshold, the nip-margin area being a marginal portion of the transfer nip through which no print medium passes, wherein, when the determination of the control section is affirmative, the power supply applies a reverse-bias voltage to the transfer member, the reverse-bias voltage having an opposite polarity to the transfer bias voltage.