The magnetic field homogeneity adjusting device (20) is characterized by comprising a magnetic field distribution measuring unit (21) for measuring the magnetic field distribution in the magnetic field space, a temperature variation calculating unit (22) for calculating the temperature variation of the ferromagnetic bodies needed to improve the homogeneity of the magnetic field space based on the measured magnetic field distribution, and a temperature control unit (12) for setting a temperature control value of the ferromagnetic bodies according to the calculated temperature variation.