[en] Method of measuring the directed velocity of plasma ions using the Fabry-Perot scanning interferometer is suggested. Measurements of the poloidal velocity of oxygen impurity ion motion have been performed under conditions of joule plasma heating in the Uragan-2 stellarator. The investigations have shown that the plasma ion velocity is directed to the side of electron diamagnetic drift and amounts to (1+-3)x10⁵ cm/s