This paper estimates new series of consumer price index (CPI) of Japan from 1900 to 1938. There has been widely used existing CPI estimated by Institute of Economic Research at Hitotsubashi University. However existing estimate used price data of Tokyo only, and left prices of other cities unused in this index. It was also calculated using Laspeyres index method, which has a bias overestimating inflation rate. We revised CPI of Tokyo from 1879 to 1938 using the same price and weight data as existing CPI, but applying superlative Fisher`s chain index instead of Laspeyres index method. In regard of price data, there are price survey reports (Bukka t?kei hy?) of 13 cities including Tokyo for the period of 1900-1939. Using this price data, we estimate regional price parity (RPP) of 12 cities, which show the price level of each city compared to Tokyo(=1). CPI of Tokyo and RPP of 12 cities, if multiplied, can yield CPIs of 12 cities for the period of 1900-1938. With CPIs of 13 cities thus attained, we integrate them into a national level one. These CPI and RPP are critical for measuring the long term trend of real wage and wage differential among regions in prewar Japan.