Abstract: An image forming apparatus includes an image carrying member to carry a toner image, a nip forming member to form a transfer nip with the image carrying member, and a transfer bias outputting unit to output a transfer bias to transfer the toner image from the image carrying member to a recording medium. The transfer bias is composed of a direct current (DC) component and an alternating current (AC) component, and a least one of the DC component and the AC component is subjected to constant voltage control. When constant current control is conducted at a timing other than when the toner image is being transferred from the image carrying member to the recording medium, a detection bias voltage at the transfer nip is detected, and the voltage of at least one of the DC component and the AC component is controlled based on the detected detection bias voltage.

Abstract: A transfer device includes a controller that controls a transfer bias supply to cause a transfer bias to increase, between an image carrier and a first rotary body disposed opposite the image carrier, a potential of the first rotary body toward an opposite polarity to a charge polarity of toner of a toner image on the image carrier to be higher than a potential of the image carrier, and to change, on the basis of identified recording medium type, a returning peak value which is one of a peak value of positive polarity and a peak value of negative polarity of the transfer bias and which generates an electric field that causes the toner having moved to the recording medium from the image carrier to return to the image carrier from the recording medium in a transfer nip.