To provide a superconducting magnet device in which cooling efficiency is enhanced by preventing/reducing intrusion of heat from a power supply terminal into the low temperature side through a copper lead.

The superconducting magnet device comprises a cryostat 10 for containing a superconducting magnet 11, and a GM (Gifford-Mc Mahon) refrigerating machine 30. The superconducting strand 12 of the superconducting magnet 11 is connected through a high temperature superconductor 13 with one end of a copper lead 14 having the other end connected with a terminal 20A which is further connected with a thermoelectric converting element 15. The terminal is connected with a power supply 40 at a normal temperature part and the GM refrigerating machine is connected, at the first stage thereof, to the high temperature side of the high temperature superconductor and, at the second stage thereof, to the low temperature side of the high temperature superconductor.