The present invention relates to a method for producing chlorinated polyvinyl chloride resin in which polyvinyl chloride resin is chlorinated by radiating ultraviolet light in a reactor into which polyvinyl chloride resin and chlorine have been introduced, wherein the radiation of the ultraviolet light is performed by using at least one light source selected from the group consisting of an ultraviolet LED, an organic EL and an inorganic EL, the light source is disposed within the reactor, at least one radiation direction of the ultraviolet light is within a range of 30° or more and 115° or less with respect to a stirring direction of polyvinyl chloride resin, and an amount of ultraviolet light radiated within the range of 30° or more and 115° or less with respect to the stirring direction of polyvinyl chloride resin is 24% or more based on a total amount of ultraviolet light radiated from the light source taken as 100%. It is thereby possible to provide a method for producing chlorinated polyvinyl chloride resin in which the reaction efficiency of the chlorination reaction is higher than a conventional method of photochlorination using a mercury lamp, and that produces chlorinated polyvinyl chloride resin having the same levels of mechanical strength and heat resistance as the chlorinated polyvinyl chloride resin produced by the conventional method.