Abstract: To provide a catalyst having hydrotreatment (hydrogenation, desulfurization and denitrification) performance that is equal to or superior to the prior art, as a hydrotreating catalyst for hydrocarbon oils, and a hydrotreating process for hydrocarbon oils using the catalyst. The catalyst comprises 10 to 40 mass % of at least one element of Group 6 of the Periodic Table, 0.5 to 15 mass % of at least one element of Groups 8 to 10 of the Periodic Table based on the oxide catalysts, and a 0.05- to 3-fold amount of an organic additive with respect to the total number of moles of the elements of Group 6 and Groups 8 to 10 of the Periodic Table, added to an inorganic porous support composed mainly of silica-alumina that comprises an oxide of a metal of Group 2 of the Periodic Table.