This study conducted an experiment on seismic retrofitting in order to improve seismic performance of RC framed structures of non-earthquake resistant designs. In the experiment, masonry infill walls were strengthened with composite precast concrete(PC) panel systems using honeycomb-type reinforcements. Structural analysis was conducted with actual structures, and a single span which was found to be in need of seismic retrofitting was scaled down by 1/2 ratio and was modeled. The specimens were of 6 different types, including the reference specimen of an RC frame designed to be non-earthquake resistant. The 6 types were divided by whether there was reinforcement on the masonry infill wall and how to retrofit the wall with the honeycomb composite panel system. The experiment results showed that seismic performance of the test specimens increased in all the factors including strength, stiffness, ductility and energy dissipation, so it was considered that retrofitting measures need to be taken to secure proper seismic performance. When seismic performance was evaluated, the target of strength and ductility was set as 30% increase. Since all the specimens were found to meet the target, it was considered proper to retrofit masonry infill walls with PC panels.