The method for reducing organic chlorine compounds in cement production facility is a method by which a quantity of organic chlorine compounds contained in powder is reduced in the cement production facility, and the method is provided with a heating step for heating the powder to separate the organic chlorine compounds from the powder or decompose the organic chlorine compounds and a gas thermal decomposing step for supplying heat-treated gas containing the organic chlorine compounds generated by heating the powder to a high temperature part of the cement production facility, thereby thermally decomposing the organic chlorine compounds contained in the heat-treated gas.