To provide a demetallization catalyst for hydrocarbon oil, which has high demetallization activity and a long service life and to provide a method for effectively hydrotreating heavy oil, which contains vanadium and nickel and has very poor quality, by using the demetallization catalyst.

The demetallization catalyst for hydrocarbon oil is obtained by depositing a group 6 metal and a group 9 metal and/or a group 10 metal in the periodic table on a fire-resistant inorganic oxide carrier (A). In the concrete, this metallization catalyst is characterized in that the group 6 metal is dispersed uniformly in the fire-resistant inorganic oxide carrier (A) and a fire-resistant inorganic oxide particle (B), which contains the group 6 metal and the group 9 metal and/or the group 10 metal, is dispersed uniformly in the fire-resistant inorganic oxide carrier (A).