A debarking mechanism including of rotatable debarking shafts extending parallel to an advancing direction (A) of the logs to be fed therethrough, which are provided with teeth extending beyond the circumferential surface of the shaft. At least the uppermost debarking shaft is moved sideways towards the inner part of the debarking mechanism in such a way that each debarking shaft directs an impact effect on logs colliding with it and moved by the debarking shafts located in a lower position. The circumferential speed of the debarking shaft is selected to be the greater the higher the debarking shaft is positioned. A free passage is arranged for the bark passing over the debarking shaft.