Abstract: Apparatus for separately sharpening the two sides of cutting edges of knife blades in slaughterhouses, butcher shops and similar establishments has a housing for a ring-shaped flexible sharpening tool and a drum-shaped carrier for the tool. The carrier is driven by a reversible electric motor. A detachable wall of the housing in front of the tool supports two discrete V-shaped blade positioning members so that the positioning members extend into the space around an annular internal sharpening surface of the tool. One side of the cutting edge of a blade is sharpened while the blade is received in one of the positioning members in such orientation that the internal surface removes material in a direction from the back toward the cutting edge.