To provide a tool which is easily prepared, settled and maintained, and by which a clam blade and a small clam blade can be easily and correctly sharpened by flattening, resharpening and a level difference in a cutting edge.

An inclined part is formed in a region of a grinding wheel. The grinding wheel is a soft material sharpening plate, and sharpened by an abrasive grain compound. The flattening of a uniform angle is performed by flexible thin flattening implements attached to a portion at uniform distance from a blade tip. A blade is sharpened into a clam shape by widening the sharpening stroke of flattening. A cutting edge of a uniform angle is sharpened by flexible resharpening implements attached to a portion at uniform distance from the blade tip. A small blade having a clam shape is attached to the blade tip by widening a stroke to the inclined part while the resharpening implements are attached. A flexible positioning gauge attracted by magnetism is fixed along a blade tip curve, and the flattening implements and the resharpening implements are loaded in a portion at uniform distances from the blade tip.