Abstract: A powder protecting three-way valve installed in a line of a semiconductor or flat panel display manufacturing apparatus to control flow of reaction by-product gas, includes: a valve casing comprising an inlet pipe through which the reaction by-product gas flows in and a plurality of outlet pipes through which the inflowing reaction by-product gas flows out in different directions; a rotating ball which is rotatably installed inside the valve casing and comprises an inlet hole communicating with the inlet pipe of the valve casing and outlet holes selectively communicating with the plurality of outlet pipes of the valve casing to control a direction of the flow of the reaction by-product gas; and a heating element installed in the valve casing to heat the inside of the valve casing.