PURPOSE: To prevent a screw blade from becoming abraded by providing a magnet at a specified interval in a spiral direction on the upper surface of the screw blade of medium stirring/grinding machine of upright type with at least either of a ground medium or a processed material being magnetizable.

CONSTITUTION: A medium stirring/grinding machine of upright type has either of a ground medium (b) or a processed material (a) by grinding as a magnetizable one. Magnets 13 are provided at a specified interval in a spiral direction on the upper surface of the screw blade 3 of a screw shaft 2. The magnet 13 attracts a ground medium (b) and a processed material (a) both being magnetizable, and the attracted ground medium (b) is magnetized and further attracts the ground medium (b). A self-lining layer A is formed by the ground medium (b) around the magnet 13 due to this progressive attraction effect. Thus, if a frictional grinding action takes place on account of a fluidized movement, the self-lining layer can be maintained to a constant thickness, resisting a frictional force with the ground medium (b), as the inner surface of a processing cylinder 1 and the upper surface of the screw blade 3 are stationary without moving vertically like a horizontal grinding machine.