Soil reinforcement technology has greatly contributed to solving seismic stability problems in soil structures. Japan has accumulated many seismic experiences, and has developed seismic technology for reinforced soil structures. This paper first introduces the concept of performance-based seismic design methods for reinforced soil walls for roads and railways in Japan. Then, in a case study of reinforced soil walls after the 2016 Kumamoto earthquake, it is shown that reinforced soil walls exhibited high performance during the earthquake. Finally, future developments in seismic design are summarized. The necessity of developing super large deformation analysis, stability analysis methods for damaged walls, and seismic risk assessments are discussed.