Abstract: Presented in this paper is the original seismic design and the seismic performance retrofit study against large-scale earthquakes of the Akashi Kaikyo Bridge. The Akashi Kaikyo Bridge is the world’s longest suspension bridge and was completed in 1998. In the original seismic design, an inland near-field earthquake with large magnitude was not considered for the seismic design force. Although the bridge encountered the Hyogo-ken Nanbu Earthquake in 1995, it was not seriously damaged since the earthquake occurred during its construction. Therefore, a seismic performance retrofit study against large-scale earthquakes has been started. In the seismic performance retrofit study, site-specific large-scale earthquakes including inland near-field earthquakes were defined based on the latest seismological information. As a result, it was found that target seismic performance was ensured by taking some minor countermeasures.