For the purpose of clarifying the tool wear of spur machine-bits (alloy steel, high-speed steel, and cemented carbide) in the machine boring of western redcedar (Thuja plicata Donn), tool-life tests were performed. After boring 1000 number of holes, the amount of tool wear was measured and the worn surface of spur edge of the bit was observed with a scanning electron microscope. From the results, the difference between in the machine boring of air-dried western redcedar and that in the machine boring of green one was determined. Potential difference was occurred between the bit and workpiece when green wood was bored in every tool material, the tool-wear progressions of high-speed steel bit and cemented carbide bit in the machine boring of green wood were faster than those in the machine boring of air-dried one. These results were completely contrary to the result of alloy steel bit. From the scanning electron microscope observation of each machine bit, it was observed that worn surface of the bit was corroded remarkably by chemical or electrochemical corrosive action.