A terminal structure of a superconducting cable conductor for connecting a terminal portion of the superconducting cable conductor with a terminal member, wherein the terminal portion comprises: a superconducting layer disposed on an outer periphery of a central support; and an insulating layer surrounding the superconducting layer, wherein the insulating layer and the superconducting layer are partially removed to expose the central support and the superconducting layer in this order from an end of the superconducting cable conductor; and wherein the terminal member comprises: a metal sleeve comprising at least one of elemental Cu, alloyed Cu, and alloyed Al, covering the terminal portion and mounted on the terminal portion, the metal sleeve comprising a first cylindrical portion, a second cylindrical portion and a third cylindrical portion which have different inner diameters, wherein: the first cylindrical portion whose inner surface is in close contact with an exposed portion of the central support, has an inner diameter larger than an outer diameter of a central support of the superconducting cable conductor; the second cylindrical portion which is soldered around an exposed portion of the superconducting layer, has an inner diameter larger than an outer diameter of the superconducting layer; and the third cylindrical portion into which the insulating layer is inserted, has an inner diameter larger than an outer diameter of an insulating layer and has a diameter-increasing portion where an inner diameter gradually increases towards an edge of the third cylindrical portion, and wherein the insulating layer comprises a wound insulating tape having a width; and a length of the third cylindrical portion is greater than a width of the insulating tape, and wherein the wound insulating tape is formed by craft paper, semi-synthetic paper or synthetic paper. a superconducting layer disposed on an outer periphery of a central support; and an insulating layer surrounding the superconducting layer, wherein the insulating layer and the superconducting layer are partially removed to expose the central support and the superconducting layer in this order from an end of the superconducting cable conductor; and a metal sleeve comprising at least one of elemental Cu, alloyed Cu, and alloyed Al, covering the terminal portion and mounted on the terminal portion, the metal sleeve comprising a first cylindrical portion, a second cylindrical portion and a third cylindrical portion which have different inner diameters, wherein: the first cylindrical portion whose inner surface is in close contact with an exposed portion of the central support, has an inner diameter larger than an outer diameter of a central support of the superconducting cable conductor; the second cylindrical portion which is soldered around an exposed portion of the superconducting layer, has an inner diameter larger than an outer diameter of the superconducting layer; and the third cylindrical portion into which the insulating layer is inserted, has an inner diameter larger than an outer diameter of an insulating layer and has a diameter-increasing portion where an inner diameter gradually increases towards an edge of the third cylindrical portion, and the first cylindrical portion whose inner surface is in close contact with an exposed portion of the central support, has an inner diameter larger than an outer diameter of a central support of the superconducting cable conductor; the second cylindrical portion which is soldered around an exposed portion of the superconducting layer, has an inner diameter larger than an outer diameter of the superconducting layer; and the third cylindrical portion into which the insulating layer is inserted, has an inner diameter larger than an outer diameter of an insulating layer and has a diameter-increasing portion where an inner diameter gradually increases towards an edge of the third cylindrical portion, and