Method of isomerizing light hydrocarbon oil

A process for isomerizing a light hydrocarbon oil having an organosulfur content as determined by coulometric titration of from 100 to 1,000 mass ppm, which process comprises:

• subjecting the light hydrocarbon oil to a hydrogenation treatment for converting an organosulfur component in the light hydrocarbon oil into hydrogen sulfide to give an organosulfur content of from 0 to 30 mass ppm as a pretreatment step;
• and
• isomerizing the light hydrocarbon oil still containing the converted hydrogen sulfide in the presence of a solid super strong acid catalyst under conditions at a temperature of from 190 to 300° C., a pressure of from 1 to 50 kg/cm2g, an H2/oil ratio of from 180 to 1800 liter/liter, and an LHSV of from 2 to 10 hr−1 as an isomerization step, wherein said solid super strong acid catalyst is a solid catalyst which has deposited thereon a super strong acid having higher acidic properties than 100% sulfuric acid.