There is provided a novel, useful dehydroxyfluorination agent containing sulfuryl fluoride (SO2F2) and an organic base that is free from a free hydroxyl group in the molecule. According to the present dehydroxyfluorination agent, it is not necessary to use perfluoroalkanesulfonyl fluoride, which is not preferable in large-scale use, and it is possible to advantageously produce optically-active fluoro derivatives, which are important intermediates of medicines, agricultural chemicals and optical materials, for example, 4-fluoroproline derivatives, 2′-deoxy-2′-fluorouridine derivatives, optically-active α-fluorocarboxylate derivatives, and monofluoromethyl derivatives, even in large scale.