Torsional vibration is likely to occur in a symmetrical buildings consisting of independent shear walls and bare RC frames, when severe earthquake attacks and the walls and the frames yield, because the structure becomes eccentric in strength. In this paper, the authors investigate the degree of this phenomenon by two way dynamic analysis. In the analytical model, the walls are modeled to beam element in which shear deformation is taken account. Two directional elasto-plastic behavior of columns, that is, axial yielding in the wall direction and flexural yielding in another direction is considered based on the plastic theory. As the result, the torsional vibration occurs when the structure yields, however, its influence on the response is rather small. Lateral displacement of the end walls is 1.4 times larger than that at the center of gravity due to the torsional deformation in the analysis.