Abstract: According to the method for producing bis(fluorosulfonyl)imide of the present invention, first, an unreacted mixed liquid is prepared by mixing a first fluorosulfonic acid with urea in a condition free of a chemical reaction between the first fluorosulfonic acid and urea. Then, the unreacted mixed liquid is dripped into a heated second fluorosulfonic acid or a heated bis(fluorosulfonyl)imide, allowing a chemical reaction between fluorosulfonic acid and urea to proceed. In this method, generation of carbon dioxide gas and heat during the chemical reaction can be controlled.