To obtain a novel fluorine-containing isocyanate which is high in its reactivity with an organic polymer, capable of giving an organic polymer water-repellent and oil-repellent properties, antistaining, weather-resistance, durability, having a favorable range of solubility in solvents and useful as a polymer modifier.

This isocyanate is represented by formula I (Rf is a 4-16C perfluoroalkyl; X is Cl, Br, I, methoxy, ethoxy; R is a group of formula III, a group of formula IV, naphthalene 1,5-diyl, 3,3'-dimethyldiphenylmethan-4,4'-diyl, hexamethylene, phenylene, cyclohexylene) or of formula II, typically 7-methoxy-8 {[N-(3-isocyanatomethyl-3,3,5-trimethyl)cyclohexyl]carbamoyl}oxy-(2- perfluorooctylethyl)-3,4,7,8-tetrahydro-dicyclopentadiene. A compound of formula I or formula II is prepared by ring-opening the epoxy ring in a compound of formula V with hydrogen chloride or methanol, followed by reaction of the ring-opened product with a diisocyanate of the formula OCN-R-NCO.