The superconducting magnet device reduces the number of connections within and/or the number of wires leading out of a superconducting coil winding and promptly starts expending the magnetic energy in a superconducting coil operating in a persistent-current mode when the superconducting coil increases in temperature or transitions to normal conductivity. This invention provides a superconducting magnet device that has the following: a superconducting coil connected to an excitation power supply; a persistent-current switch connected to the superconducting coil; a heater that controls the temperature of the persistent-current switch; a current source that is connected in parallel with the persistent-current switch and has a different polarity from the excitation power supply; a driving circuit connected to the heater and the current source; and a signal-inputting means for inputting a signal to the driving circuit. The driving circuit operates the heater and the current source when the signal is inputted thereto.