PURPOSE: To improve the operating ratio by a method wherein after a hydrocarbon feeding raw material contg. asphaltenes, sulfur impurities and metal impurities is transferred to a specified alternating zone or a reactor, it is hydrodemetallized and then, hydrodesulfurizated.

CONSTITUTION: A hydrocarbon feeding raw material contg. asphaltenes, sulfur impurities and metal impurities is transferred to an operating one of two alternating zones or reactors 5 and 6 which are operated alternately and contain fixed beds 24 and 25 of hydrodemetallizing catalyst consisting of a carrier and a metal (a compd.) selected from the periodic table V, VI and VIII groups and are arranged in parallel from a pipeline 1 and is passed with hydrogen through at least one hydrodemetallizing reactors 26 and 27 with the hydrodemetallizing catalyst to perform hydrodemetallization and then, is passed with hydrogen through at least one hydrodesulfurization reactors 28 and 29 contg. hydrodesulfurization catalyst to perform hydrodesulfurization. When one of alternating zones or the reactors 5 and 6 does not function, another one is operated.