In order to make it possible to improve the homogeneity of a magnetic field and suppress upsizing of a device as a whole, a current-variable correction coil (4) which generates a magnetic field for correcting the homogeneity of a magnetic field generated by a main coil (2) formed by winding an ReBCO based superconducting wire rod is provided inside the main coil (2). The magnetic field generated by the current-variable correction coil (4) is little affected by a shield current flowing through a superconducting layer of the ReBCO based superconducting wire rod.
