PURPOSE: To facilitate replacement operation for a friction resisting piece in a screw conveyer for a screw centrifugal separator by fixing the friction resisting piece along the longitudinal outer peripheral edge of the screw in such a manner as to oppose centrifugal force by engagement with difference in level.

CONSTITUTION: A fixing piece 34 having a stepped portion 35 is welded to the outer periphery of a screw blade 21. A friction resisting piece 22a comprises a wear-resisting member 31 such as a tungsten carbite or the like deposited on a metallic backplate 30 having a stepped portion 32. The friction resisting piece 22a is secured to the fixing piece 34 with bolts 37 to fix the friction resisting piece 22a along the outer peripheral edge of a screw 23. In this arrangement, the friction resisting piece can be replaced only by detaching and attaching the bolts 37 to facilitate the replacement work.