To decrease the reflux rate and improve the conversion rate of hydrocarbon, wherein a portion of introducing a hydrocarbon material into a distillation column is drawn into a hydrogenation reactor placed at the outside of the distillation column to be hydrogenated followed by re-introduction into the distillation column at a higher position than the drawing position and at a lower temperature than the drawing temperature with continuous distillation.
When treating within a zone generating a vapor-distilled fraction of the top part and effluence of the bottom part after introducing a hydrocarbon material into a distillation column 2 through a duct 1, the liquid drawn through the duct 15 is hydrogenated with hydrogen through a tube line 4 followed by transporting said liquid into the top part of a hydrogenation reactor 3 where a conversion reaction of a portion of the hydrocarbon material (e.g. benzene) is performed. Then, after cooling effluence of reactor 3 preferably at least 10°C lower than the drawing temperature in a heat-exchanger 16, the cooled effluence is re-introduced into the distillation column 2 through the duct 17 at a higher position than that of the drawing tube line 15. As a result, this can also lead to reduction of the distillation zone size.