PURPOSE: To prepare objective salt water and an acid soln. by executing charging and regenerating processes of an ion exchange resin in another vessel of columnar shape and executing ion exchange with the salt water and the acid soln.

CONSTITUTION: A resin taken from a column 10 and containing the salt water taken out of a column 10 is transferred into a vertical columnar vessel 14 and double bottoms of lattice shape are provided at the vessel 14 to hold the resin and pass liquid therethrough. After the salt water is drained, the resin is washed with water taken out of a pipe 15 and entering through a pipe 16 until the salt is removed. The salt is further dissolved by using a dilute soln. taken out of the pipe 15 and is reused after concentration is adjusted. The resin washed and drained in the vessel 14 can be used at a second stage of the process. For this purpose, the resin is transferred into a vessel 23 by being carried with the salt water which is obtained at a column 20 and enters through a pipe 27.