The invention refers to the engineering industry and in particular — mechanisms with unbalanced rotors and their automatic balancers. The invention is a rotor balancing device which comprises a toroidal housing containing at least two spherical bodies. The acceleration surface of the spherical bodies on the inside of the housing is designed coarser than the operating surface on the periphery of the inside surface of the housing, and it is additionally treated by polishing it, thereby ensuring minimum rolling friction between the spherical bodies and the balancing device during operation. This ensures that devices with unbalanced rotating masses reach optimum operating conditions faster, and vibrations during the transitional and operating mode are reduced. The invention can be used in washing machines with centrifuges, in industrial centrifuges, hand-held instruments, CD/DVD players and in other applications.