PURPOSE: To carry out reaction, crystallization, filtering and drying in a single tank, by providing a filter plate to the upper part of a shaft type cylindrical tank, a stirring blade to the lower part thereof and heating medium jackets to the side surface and the undersurface thereof.

CONSTITUTION: Heating medium jackets 6 are provided to the side surface and the undersurface of a shaft type cylindrical tank 1 freely rotated around a horizontal shaft and a filter plate 12 is provided to the upper part thereof to form a filter chamber 13 and a stirring blade 21 is provided to the lower part in the tank 1. By using this tank 1, reaction and crystallization are carried out under such a condition that the filter plate 12 is mounted to the upper part of the tank, filtering is carried out under such a condition that the tank 1 is rotated 180° to position the filter plate 12 to the lower part thereof and, after a cake formed on the filter plate 12 is scraped off by the stirring blade 21 under such a condition that the tank 1 is again rotated 180° to restore the same, drying is carried out by heating the jackets 6. As described above, reaction, filtering and drying are carried out in good operability in a single tank.