In this paper, an experimental research was carried out to compare the capability to control a MR-damper attached structure, which turned out to differ according to its vibration control direction whether vertical or horizontal. The target structure for the experimental test was a real size asymmetrical cable-stayed bridge. The MR-damper for vibration control was designed 30KN to fit into the target bridge. For the performance experiment of the MR-damper, the el-centro earthquake wave using three shaking table was inflicted on the model bridge structure, once horizontally and then vertically. Finally, each control capability, different according to its direction, was compared and evaluated. The experiment proved that the MR-damper was able to damp in a different way according to its control direction(horizontal or vertical) and also to work effectively damping the acceleration responses of the structure.