A process for producing 3,4-dichloro-5-cyanoisothiazole represented by a general formula (3): [Chemical Formula 18] the process comprising； reacting a nitrile compound represented by a general formula (1): [Chemical Formula 16] (wherein "n" denotes an integer of 0 to 2), with sulfur chloride represented by a general formula (2): [Chemical Formula 18] SmCl2 (2) (wherein "m" represents an integer of 1 to 2), or a mixture thereof in an aprotic polar solvent. There is provided a process for producing 3,4-dichloro-5-cyanoisothiazole, which is capable of suppressing by-production of a waste, without using a raw material having a having a strong toxicity； and is capable of providing a product having a higher purity in a high yield and efficiency in an industrial scale, in a simple manner.
