PURPOSE: To eliminate a thrust force between shafts and to obviate a thrust bearing by concentrically disposing magnets of driven and driving sides through a cylindrical wall.

CONSTITUTION: A shaft 16 is rotated by a motor. A magnet 18 of driving side secured to the upper end of the shaft 16 is rotated inside the cylindrical wall 4 of an intermediate cylinder 5 secured to the bottom of an agitating vessel. As a result, a magnet 12 of a driven side magnetically coupled to the magnet 18 is rotatably driven together with a supporting cylinder 9 outside the wall 4, and rotated by a shaft 8 coupled to the cylinder 9. Agitating blades are secured to the top of the shaft 8.