In order to suppress fringe field due to the magnetic field generated from shield coils along the center axis of main coils and the shield coils that are disposed with their center axes being identical, when reducing fringe field to the outside of a magnet apparatus using the shield coils, the magnet apparatus is configured so that the radii of the main coils are approximately equal to or smaller than the radii of the shield coils, the radii of auxiliary coils are smaller than the radii of the shield coils, the distance between the two main coils is smaller than the distance between the two shield coils, and the distance between the two shield coils is smaller than the distance between the two auxiliary coils.