PURPOSE: To easily synthesize in large quantities the title compound useful as a raw material for medicines etc., by making phosgene act on pyrrole as readily available raw material followed by hydrolysis.

CONSTITUTION: Firstly, phosgene is made to act on pyrrole as raw material. In this case, the phosgene is gradually either dripped or blown into the reaction system at pref. 0°C to room temperature. After phosgene addition, the system is agitated for about twenty-four hours, and finally, to complete the reaction, the system is further heated and refluxed. Thence, the reaction product is hydrolyzed to obtain the objective compound. Specifically, the reaction product is added to an aqueous solution of an inorganic base such as NaOH followed by extractive separation using an organic solvent. An inorganic acid such as hydrochloric acid is then added to the resulting aqueous layer followed by extraction with an organic solvent, and the resulting organic layer extracted is dried and filtered, and then the organic solvent is distilled off. The phosgene can be prepared by making a base act on trichloromethylchloroformate.