Seismic performance check and seismic retrofit study against a Level-2 ground motion was performed for an existing upper-deck type steel arch bridge. Dynamic analysis with geometric and material nonlinearities was carried out by using a 3D fiber model. The allowable value of main members such as arch ribs was verified from serviceability point of view after earthquake by FEM analysis. As a result, the main members were remained elastic. For the sway bracing and lower lateral bracing caused transverse buckling and thus reduced strengths, an efficient retrofitting method by energy absorption is proposed to prevent these buckling.