A hydrotreating catalyst for heavy oil, comprising an alumina carrier and both a Group 6 metal component and a Group 9 or 10 metal component supported on the carrier. The alumina carrier contains 0.5 to 20 wt.% (based on the catalyst) of silica, which is dispersed therein in the form of silica particles having a mean particle diameter of 0.05 to 1 mu m. The catalyst has a pore diameter distribution of pore diameters of 600 ANGSTROM or below and a median pore diameter of 70 ANGSTROM to less than 150 ANGSTROM . The catalyst exerts excellent desulfurization and denitrification characteristics for a long period when used in hydrotreating hydrometallized heavy oil.