Disclosed is a method for producing a bis(fluorosulfonyl)imide, which comprises: a preparation step wherein urea is added to first fluorosulfuric acid without being reacted with the first fluorosulfuric acid, thereby preparing an unreacted liquid mixture; and a drop reaction step wherein the unreacted liquid mixture is dropped into and reacted with heated second fluorosulfuric acid or a heated bis(fluorosulfonyl)imide. The method is capable of controlling the generation of a carbon dioxide gas and the reaction heat.
