PURPOSE: To prevent the generation of a low pressure region by producing an additional flow in a tank by arranging a stirring wing formed as a propeller on an impeller head and further a flow generation section in a lower region.

CONSTITUTION: An impeller head rotating by non-contact type drive using magnetic force is externally fitted and held to a conical body 6 projectingly provided inside a tank 4. A propeller type stirring wing 3 is arranged on the impeller head 2 so as to produce an upwardly directing flow and a flow generating section is arranged in a lower region of the impeller head 2 so as to produce a flow directing downward or to the side. Consequently, although a liquid in the tank 4 is stirred by the stirring wing 3, and falls in the center and rises in the peripheral by centrifugal force, the liquid is transferred upwardly by a rotation into torsion direction, improving a lower pressure region, preventing a drawing action of gas and preventing generation of bubbles. A groove 13 is formed as a flow generation section to clean a liquid in a hollow section 15 by extracting and to add a downward axial force of the impeller head 2.