A connecting structure for a superconducting device, comprising: a refrigerant container having an open upper part, the refrigerant container including at a lower part thereof a cryogenic part configured to contain a liquid refrigerant, and a temperature gradient part provided above the cryogenic part and configured to contain a gaseous refrigerant, wherein the gaseous refrigerant has a temperature gradient; a vacuum container configured to cover the refrigerant container so as to vacuum insulate the vacuum container; a sensor port provided on the refrigerant container while passing through the vacuum container, the sensor port including at least one sensor detachably provided to sense temperature of the refrigerant container or temperature of a refrigerant contained in the refrigerant container; a purge port configured to supply an inert gas into the sensor port or apply sound pressure into the sensor port, the purge port being provided on an outer wall of the vacuum container; a room-temperature part tubular body configured to contain insulating oil or an insulating gas, the room-temperature part tubular body forming a room-temperature part and being separated from the refrigerant container; a sealing member configured to seal the open upper part of the refrigerant container to separate the temperature gradient part from the room-temperature part; and a conductor wire couplable to a superconducting conductor layer of a superconducting cable in the liquid refrigerant contained in the refrigerant container, the conductor wire extending to the room-temperature part tubular body while passing through the sealing member. a refrigerant container having an open upper part, the refrigerant container including at a lower part thereof a cryogenic part configured to contain a liquid refrigerant, and a temperature gradient part provided above the cryogenic part and configured to contain a gaseous refrigerant, wherein the gaseous refrigerant has a temperature gradient; a vacuum container configured to cover the refrigerant container so as to vacuum insulate the vacuum container; a sensor port provided on the refrigerant container while passing through the vacuum container, the sensor port including at least one sensor detachably provided to sense temperature of the refrigerant container or temperature of a refrigerant contained in the refrigerant container; a purge port configured to supply an inert gas into the sensor port or apply sound pressure into the sensor port, the purge port being provided on an outer wall of the vacuum container; a room-temperature part tubular body configured to contain insulating oil or an insulating gas, the room-temperature part tubular body forming a room-temperature part and being separated from the refrigerant container; a sealing member configured to seal the open upper part of the refrigerant container to separate the temperature gradient part from the room-temperature part; and a conductor wire couplable to a superconducting conductor layer of a superconducting cable in the liquid refrigerant contained in the refrigerant container, the conductor wire extending to the room-temperature part tubular body while passing through the sealing member.