A superconductive magnet comprised of a bulk member or sheet member of a type II superconductive material, wherein a distribution of the magnetic flux density component vertical to the surface directly above the surface of the bulk member or sheet member (a) has a maximum value at a center of said bulk member or sheet member and is about zero at its side edge, and (b) has at least one minimal value point between said center and side edge. A superconductor is cooled to not more than a critical temperature after applying a magnetic field Hex1 [A/m] near the magnetic field generation system in the normal conductive state, then the applied magnetic field is reduced to zero, then a magnetic field is applied until the applied magnetic field becomes −Hex2 [A/m] in the opposite direction to the trapped magnetic flux to make the trapped magnetic flux density Bin0 [T], then the applied magnetic field is again returned to zero, where Hex1>0 and Hex2>0.