A superconducting wire having a stacked structure comprising (a) a substrate composed of an electrically conductive material, (b) an oxide superconductor material, and (c) an electrically conductive material which is substantially not reactive with said oxide superconductor material (b), wherein said electrically conductive material (c) is impregnated in said oxide superconductor material (b) by way of heat fusion such that gaps among crystal grains contained in said oxide superconductor material (b) are filled with said electrically conductive material (c). And a process for the production of said superconducting wire.