This report briefly describes the outline of geology and chemical property of ground water in Western Osaka. In the central area the main aquiferous strata are found at the depths of 30 - 40m,60 - 70m,100m or even at the greater depths from the ground surface. Correlation of these strata were made. The panel diagram which was made from the records of well drilling shows that the 1st aquiferous stratum (W.1) crops out in the Itami hills and at the west foot of the Uemachi hills. Near the Uemachi hills the 2nd aquiferrous stratum (W.2) underlies with or without a markedly clayey stratum between them. Changes in character of water were examined by (1) local variation of near by arranged wells, (2) seasonal variation, and (3) depth of aquifer. On the basis of these fundamental investigations, the distribution maps of major chemical constituents of water were made on W.1 and W.2.