The invention discloses a tool protection casing. The tool protection casing comprises a body made from stainless steel pieces. The body is provided with a first folding pressing mark. The body is divided into a rectangular portion and a square portion through the first folding pressing mark. A second folding pressing mark is arranged at the position, located at a diagonal line, on the square portion. The top end of the second folding pressing mark intersects with the top end of the first folding pressing mark. A blade outlet is formed in the square portion. The central line of the blade outlet coincides with the second folding pressing mark. The using process of the tool protection casing is simple; the whole mass is small; work intensity of operating workers is lowered; and production efficiency is improved. Meanwhile, a majority of a blade is shielded, and the risk of hurting users and people around in the using process of a tool is lowered. The protection casing can be matched witha majority of cutter blades on the market; the high cost and maintenance difficulty caused by use of special relieving tools are avoided; and universality is quite good.