A strong-magnetic-force field generating device is provided which can increase a magnetic force field and which can make the magnetic force field spatially uniform without adding an additional superconducting magnet to a commercially-available superconducting magnet. In the strong-magnetic-force field generating device, a disc ferromagnetic element is arranged inside a bore and above the equatorial plane thereof in a solenoid superconducting magnet, whose central axis is directed in a vertical direction, so as to be symmetric with respect to the central axis; and a ring ferromagnetic element is arranged above the disc ferromagnetic element so as to be out of contact with the disc ferromagnetic element and so as to be symmetric with respect to the central axis.