To provide a method for treating exhaust gas containing a hydrogen chloride capable of recovering a refined hydrochloric acid having high purity without difficulty in an operation caused by adherence of an organic material adhered or generated from a melted vinyl chloride to a furnace wall or the like in the case of dry distilling a waste plastic containing a vinyl chloride resin and recovering the acid.

A waste plastic containing a vinyl chloride resin and a powder coke having a particle size of 10 mm or below are charged at a predetermined ratio in a rotary kiln 1, dry distilled in an insert gas atmosphere, and exhaust gas generated when dry distilled is burned at 800°C or above with the coke and char existing in the gas as main fuels in a combustion furnace 2. Thus an organic material contained in the gas is mineralized, combustion exhaust gas generated from the furnace is dust removed by a dust remover 3, then crude hydrochloric acid is recovered in an absorption tower 7, and the recovered acid is distilled to an industrial hydrochloric acid or a hydrochloric anhydride.