The present invention provides an image forming apparatus comprising an image forming unit configured to form an image on an image carrier, a transfer unit configured to transfer the image formed on the image carrier onto a transfer medium, a voltage applying unit configured to apply a voltage to the transfer unit, a current detection unit configured to detect a current that flows through the transfer unit when the voltage applying unit applies the voltage, and a control unit configured to control the voltage applying unit based on a detection result of the current detection unit.