To provide a desulfurization process of a hydrocarbon oil excellent in handleability, operationability, cost effectiveness, mass-productivity and productivity by which a low sulfur hydrocarbon oil with a sulfur content as low as about 10 ppm or lower or a sulfur-free oil is obtained by efficiently eluting organosulfur compounds in the hydrocarbon oil into a solvent and separating them and dibenzothiophenes in the solvent are converted into dibenzothiophene sulfones having a high added value and organosulfur compounds are efficiently and easily recovered in a high purity as useful resources by separating the sulphones from the solvent.

The desulfurization process of a hydrocarbon oil comprises a solvent contact step in which a hydrogenated refined oil obtained by hydrogenation-desulfurizing the hydrocarbon oil is brought into contact with a solvent and organosulfur compounds included in the hydrogenated refined oil are eluted into the solvent and a separation process in which the sulfur-containing solvent into which the organosulfur compounds have been eluted and the desulfurized oil from which the organosulfur compounds have been removed are separated.