A process for producing an alkoxycarbonylfluoroalkanesulfonate represented by the formula [1] is provided. This process includes the steps of (a) reacting a halofluoroalkanoate represented by the formula [2], with a sulfinating agent, thereby obtaining an alkoxycarbonylfluoroalkanesulfinate represented by the formula [3]; and (b) reacting the alkoxycarbonylfluoroalkanesulfinate with an oxidizing agent, thereby obtaining the target alkoxycarbonylfluoroalkanesulfonate. Furthermore, it is possible to react the obtained alkoxycarbonylfluoroalkanesulfonate with a monovalent onium salt to conduct a salt exchange, thereby obtaining a alkoxycarbonylfluoroalkanesulfonic acid onium salt represented by the formula [4]. ##STR00001##