Recently, considerable interest has developed in surfactant additives for use in district heating and cooling systems to lower pumping energy requirement. We already reported the drag reduction for an enclosed rotating disk in surfactant solution. On the other hand, it is not cleared that the mechanism of the drag reduction for the frictional resistance of the rotating disk in surfactant solutions. In this study, it is clarified that the effects of surfactant additives on the flow around the rotating disk from flow visualization. Experiments were carried out by means of aluminum and tufts techniques. Test surfactant solution was Ethoquad O/12 with sodium salicylate at concentrations of 200ppm and temperature was 18℃. Consequently, it has been clarified that the amplitude of circular vortex over the rotating disk was reduced and the flow direction near the disk was turned to outward by the surfactant solution.