PROBLEM TO BE SOLVED: To obtain a new detection method which does not depend on the intensity of a magnetic field, since need for structural analysis for complicated compounds whose molecular weights are large has become stronger with recent development of protein research, consequently performances required for NMRs become severer year by year, the center magnetic fields of the NMRs increase for making detection sensitivity higher, and sensitivity increase gradually approaches its limit in an existing system. SOLUTION: The shape of a detecting coil is changed from a conventional birdcage type 27 to a solenoid system 4 which has a higher sensitivity. As a result, a superconductive magnet is made up of split magnets by superconductive magnets 1, 2, 3 which are split right and left, and generate 11 T, favorably 14.1 T or more in a horizontal direction, instead of conventional multilayer air-core solenoids 28, 29, 30. The uniformity of a magnetic field is lowered below 0.001 ppm, and its time stability is lowered below 0.001 ppm.
