This paper presents the seismic retrofit practice of existing highway bridges in Japan. At first, the histories of the past seismic design codes, past seismic evaluation, and past seismic retrofit practices for highway bridges are described. Then the damage caused by the 1995 Hyogo-ken Nanbu Earthquake and the lessons learned from the earthquake are briefly described. Finally, the seismic retrofit program after the Hyogo-ken Nanbu Earthquake is described with emphasis on research and development as well as the seismic retrofit practice of existing reinforced concrete highway bridges.