PURPOSE: To obtain light products of high quality by deasphalting a residual hydrocarbon oil and then, subjecting the deasphalted oil to thermal, cracking to efficiently carry out the conversion of the residual hydrocarbon oil.

CONSTITUTION: The conversion of a residual hydrocarbon oil is carried out by the steps of deasphalting a residual hydrocarbon oil such as a heavy asphaltene-containing hydrocarbon containing not less than 75 (wt.)% hydrocarbons having a boiling point of not lower than 520°C in a deasphalting zone 101 to obtain (i) a deasphalted oil (DAO) at a yield of at least 50%, preferably 60-90%, more preferably 65-85%, based on the total weight of residual hydrocarbon oil and (ii) an asphaltene fraction; and passing part or all of the DAO through a thermal cracking zone 102 to thermally crack it at a temperature of 350-600°C under a pressure of 1-100 bar at an average residence time of 0.5-60 min so that a 520°C+ conversion of at least 60%, preferably 70-90%, based on the total weight of materials having a boiling point of not lower than 520°C present in the DAO before thermal cracking is obtained.