A superconductive cable core comprising a superconductor and an insulation layer covering the outer circumference of the superconductor is provided. The superconductive cable core is sectioned in the longitudinal direction into a cable portion, and connection structure forming portions located at the opposite ends of the cable portion to form reinforcing insulation structures when they are connected with an other conductive member. The connection structure forming portion at least occupies the portion of the superconductive cable core ranging from the end of the superconductive cable core to the end of the reinforcing insulation structure. When insulation performance of the insulation layer at the connection structure forming portion is set higher than that at the cable portion, the superconductive cable core can form a highly reliable joint even if insulation design of the cable itself with sufficient allowance is not possible.