PURPOSE: To simplify the titled apparatus and to cut down the cost by incorporating the function of a settler into a crystallizer to eliminate the settler and the piping whiich are needed by an existing settler.

CONSTITUTION: Plural partition walls 21 are provided radially in the space between a baffle tube 7 and the shell wall 1a over the whole height of the settling region to constitute plural chambers 6a, 6b and so on between the shell wall 1a and the partition wall 21 so that the settling region may be divided into plural sections. The plural baffle plates 22, which are lower than the partition wall 21, are also provided radially between the lower part of the baffle tube 7 and the shell wall 1a, and a clarified mother liquor discharging pipe 17 is communicated and connected with the upper part of the shell wall 1a on the chamber 6b side which is provided with the baffle plate 22. A circulation pipe 16 is communicated and connected with the upper part of the shell wall 1a of the other chamber 6a. Accordingly, since the clarified mother liquor, contg. a small amt. of solid component, can be taken out from the clarified mother liquor discharging pipe 17, the settler and the piping needed by the existing thickener are made unnecessary.