TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The solid acid catalyst consists of zeolite chosen from proton-type faujasite-type zeolite, proton-type mordenite and proton-type beta-zeolite. The solid acid catalyst is a catalyst consisting of a solid super strong acid chosen from sulfate radical zirconia, sulfate radical alumina, sulfate radical tin oxide, sulfate radical iron oxide, tungstic acid zirconia and tungstic acid tin oxide. The transition metal oxide is copper oxide.Preferred Property: The solid super acid catalyst has specific surface area of 100 m2/g or more.Preferred Composition: The silica/alumina ratio of faujasite-type zeolite, mordenite and beta-zeolite is 100 mol/mol or less. The positive ion content other than faujasite-type zeolite, mordenite and proton of beta-zeolite is 5 mass% or less.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: Sulfur compounds contained in hydrocarbon oil and/or sulfur compound and aromatic hydrocarbon are reacted by making hydrocarbon oil and solid acid catalyst contact. Desulfurizing is performed such that the concentration of total sulfur compound contained in the hydrocarbon oil is 1 ppm or less. The hydrocarbon oil has aromatic hydrocarbon as main component. The aromatic hydrocarbon is at least one type chosen from benzene, 7-14C alkyl benzene, naphthalene and 11-18C alkyl naphthalene. The hydrocarbon oil is kerosene or light oil.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Catalyst: The solid acid catalyst consists of zeolite chosen from proton-type faujasite-type zeolite, proton-type mordenite and proton-type beta-zeolite. The solid acid catalyst is a catalyst consisting of a solid super strong acid chosen from sulfate radical zirconia, sulfate radical alumina, sulfate radical tin oxide, sulfate radical iron oxide, tungstic acid zirconia and tungstic acid tin oxide. The transition metal oxide is copper oxide.Preferred Property: The solid super acid catalyst has specific surface area of 100 m2/g or more.Preferred Composition: The silica/alumina ratio of faujasite-type zeolite, mordenite and beta-zeolite is 100 mol/mol or less. The positive ion content other than faujasite-type zeolite, mordenite and proton of beta-zeolite is 5 mass% or less. EXAMPLE - Solid acid catalyst (H-Y type zeolite) (with silica to alumina ratio of 6 mol/mol, specific surface area of 550 m2/g, crystalline diameter of 0.2-0.4 microns and particle diameter of 6-8 microns) (in g) (1) was contacted with benzothiophene (4) diluted to 10 mass% with toluene. Subsequently, supernatant liquid was extracted at room temperature, and sulfur contained in benzothiophene was desulfurized.