This method for regenerating and utilizing a heavy-oil desulfurization catalyst is characterized by comprising: the step of withdrawing, from one of heavy-oil desulfurization devices, a heavy-oil desulfurization catalyst in which the permissible metal amount (MPr1), indicated by the following equation (1), is below 0; the step of regenerating the withdrawn heavy-oil desulfurization catalyst; and the step of filling the regenerated heavy-oil desulfurization catalyst into at least one of the other heavy-oil desulfurization devices. · MPr1 = (PV/2Vv)×{8×105×(PD)1.3}×(Sp/Vp)-(VA1+VA2) Here, PV is the pore volume of the catalyst in the fresh state; Vv is the volume of vanadium, in terms of the volume of vanadium sulfide, at the time when 1 mass% vanadium has accumulated on 1 kg of the fresh catalyst; PD is the average pore diameter of the catalyst in the fresh state; Sp is the average outer-surface area per particle of the catalyst in the fresh state; Vp is the average volume per particle of the catalyst in the fresh state; VA1 is the amount (mass%) of vanadium accumulated in the preceding device; and VA2 is the amount of vanadium accumulated in the case where the regenerated catalyst is used in the same device.