To provide a plaster slurry stirring machine capable of controlling slurry density by its operational control, and to provide a stirring method therefor.

A plaster slurry stirring machine (10) comprises: a slurry inflow port; a slurry delivery port; a cylindrical housing (20); a rotary driving shaft (30); and a rotor (40). The rotor is provided with: a plurality of rotary blades (42) extending from the central part (41) of the rotor to the outer direction; and flipper parts (43) integrated with the rotary blades and each partially occupying the region in a space with the rotary blade. The density of the plaster slurry fed to the surface of a plaster board paper is regulated by the control of the rotational speed of the rotor.