Seismic evaluation and retrofitting of existing RC buildings are very important for earthquake disaster mitigation for Myanmar because almost all RC buildings in Myanmar have been built without national building codes and seismic designs. In this study, the Japanese seismic evaluation method is studied and applied to one Japanese building and one Myanmar building in order to introduce these evaluation methods into Myanmar in the future. To verify the seismic evaluation methods, the responses of two buildings are performed for the nonlinear frame analysis with STERA 3D program again. After analyzing data by STERA 3D program, the results are also coincided with the seismic evaluation methods. After evaluation, both target buildings are found to be weak in seismic performance. Simple retrofit methods such as wing walls, RC shear walls and structural slits are chosen to increase their seismic capacity. After retrofit, enough seismic capacity is obtained in both target buildings.