A superconducting cable joint structure (52, 54) is a structure used to joint together superconducting cables (100) used at cryogenic temperature or to joint together a terminal of the superconducting cable (100) and a normal conducting cable (33), and it includes a joint insulation layer (20) arranged radially outer than a portion (22) connecting the superconducting cables' respective conductors (11) together or the superconducting cable's conductor (11) and the normal conducting cable's conductor (31) together, and at least one coolant path (S) provided at the joint insulation layer (20) to cool the portion connecting the conductors together. The cable cores can have their connection prevented from generating heat to have an increased temperature.