A pretreatment mixing and stirring device, arranged at a stage prior to a slurry formation mixing and stirring device which forms a gypsum slurry by kneading a calcined gypsum and water, and performing a pretreatment by mixing a calcined gypsum with one or more kinds of additives selected from liquids and powders, comprising:
- a cylindrical housing having a top plate, a bottom plate arranged to oppose to the top plate, a side plate arranged between the top plate and the bottom plate, and a mixing and stirring region where the calcined gypsum and the additive are mixed and stirred in an interior surrounded by the top plate, the bottom plate, and the side plate;
- a disk-shaped rotating plate arranged inside the housing;
- a rotating drive shaft, penetrating the top plate or the bottom plate of the housing, and coupled to the rotating plate;
- a calcined gypsum supply port, arranged in the top plate, and configured to supply the calcined gypsum to the mixing and stirring region;
- and
- an additive supply port, arranged in one of or both of the top plate and the side plate, and configured to supply the additive to the mixing and stirring region.