The Great East Japan Earthquake of March 11, 2011, incurred huge damages to Japan. This paper investigates how this earthquake influenced the value of Japanese insurance companies, especially non-life insurance companies. Our findings are as follows. (1) The stock prices of insurance companies decreased right after the earthquake. The spread of this decrease was less for the stock prices of non-life insurance companies than for those of life insurance companies. (2) The more capital buffer a non-life insurance company had, the higher the stock return. (3) The Earthquake Insurance System on Dwelling Risks in Japan not only indemnifies seismic losses but also functions as a Japanese stock market stabilizer.