This paper addresses the relationship between economic development, income inequality and social stability, using the data of prewar Japan. We have made prefecture-level income inequality index, based on tax and wage statistics with respect to four data points, 1888, 1896, 1921 and 1935. Regression analyses of the prefecture-level panel data confirmed that there was an inverse-U shaped relationship between economic development and income inequality. At the same time thorough analyses of the data on thefts and suicides, we found that income inequality gave a negative impact on social stability.