[Problem to be solved] To provide an image forming apparatus for suppressing formations of white spots and achieving high quality images, while obtaining sufficient image densities in both of the recessed parts and the projected parts of a recording medium surface.[Solution] An image forming apparatus includes a transfer member 36 that abuts against a surface of an image carrier carrying a toner image and forms a transfer nip, and a power supply 39 that outputs a voltage (transfer bias) for causing the toner image on the image carrier to be transferred onto a recording medium P nipped in the transfer nip. The voltage is switched alternatingly between a transfer direction voltage for causing the toner image to be transferred from the image carrier onto the recording medium and a voltage having an opposite polarity of the transfer direction voltage when the toner image on the image carrier is to be transferred onto the recording medium. A time-averaged value (Vave) of the voltage is set to a transfer direction polarity that causes the toner image to be transferred from the image carrier onto the recording medium, and is set more in the transfer direction than a median voltage (Voff) between a maximum and a minimum of the voltage.