the present invention relates to an apparatus for treating a solution or a slurry solution and its improved types . the apparatus of the present invention comprises a hollow rotating shaft having a sealing mechanism and a rotating mechanism at upper portions thereof , the apparatus being characterized by comprising a plurality of stirring branch pipes attached to the lower end of the hollow rotating shaft vertically downward extending into the solution in a storage tank , and a plurality of gas jet pipes disposed under the respective branch pipes , the gas jet pipes extending vertically downward and being opened at the lower ends thereof , whereby the shaft and the stirring branch pipes are rotated , while a gas is jetted from openings of the gas jet pipes through the sealing mechanism , the hollow rotating shaft and the branch pipes . the improved types of the above mentioned apparatus include an apparatus in which a plurality of stirring blades are additionally provided under the branch pipes , an apparatus in which a wash water feed pipe is additionally provided in the hollow rotating shaft , and the like .