It was found that a fluoro derivative can be produced by reacting a hydroxy derivative with sulfuryl fluoride (SO2F2) in the presence of an organic base or in the presence of an organic base and “a salt or complex comprising an organic base and hydrogen fluoride”. According to the present production process, it is not necessary to use perfluoroalkanesulfonyl fluoride, which is not preferable in industrial use, and it is possible to advantageously produce optically-active fluoro derivatives, which are important intermediates of medicines, agricultural chemicals and optical materials, specifically 4-fluoroproline derivatives, 2′-deoxy-2′-fluorouridine derivatives, optically-active α-fluorocarboxylate derivatives, and the like, even in a large scale.