PURPOSE: To crack a crude oil into a light crude oil to be readily desulfurized by previously bringing a raw material crude oil subjected to pretreatment such as desalting into contact with hydrogen under a specific partial pressure of hydrogen at a prescribed reaction temperature.

CONSTITUTION: A raw material crude oil subjected to pretreatment such as desalting is brought into contact with hydrogen in a hydrogenating column under 2-50K/G (preferably 20K/G) partial pressure of hydrogen at 50-300°C (preferably 200°C) for a long time (preferably ≥10 minutes) and cracked while raising the partial pressure or temperature of hydrogen of both. By this cracking method, a high-sulfur crude oil is readily treated, gum will not be formed and water, impurities and scale in the crude oil are removed.