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.