The invention discloses a power supply device for seafloor power cable failure diagnosis capable of generating electricity through temperature difference. The power supply device for seafloor power cable failure diagnosis capable of generating electricity through temperature difference comprises a heat transmission layer, heat insulating layers, five temperature difference generating slices, a fixing ring, a heat dissipation layer and a stabilized voltage supply encapsulated circuit. The five temperature difference generating slices and one face of the stabilized voltage supply encapsulated circuit are respectively pasted on one side face of the heat transmission layer, the other faces of the five temperature difference generating slices and the stabilized voltage supply encapsulated circuit are respectively pasted with the heat dissipation layers, and the heat insulation layers are arranged between two adjacent temperature difference generating slices and between the temperature difference generating slices and the stabilized voltage supply encapsulated circuit. The temperature difference generating slices, the heat dissipation slice and the stabilized voltage supply encapsulated circuit are fixed through fixed rings. The five temperature difference generating slices are connected in series in sequence and two ends of the temperature difference generating slices are connected with the stabilized voltage supply encapsulated circuit. The power supply device for seafloor power cable failure diagnosis is capable of generating electricity through temperature difference and has the advantages of being small in size, simple in installation and maintenance work, low in cost and good in reliability of arrangement working.