PROBLEM TO BE SOLVED: To provide an easy-to-handle magnetic field adjustment device capable of performing highly accurate magnetic field adjustment, a magnet device equipped with the magnetic field adjustment device, and a magnetic field adjustment method.SOLUTION: A magnetic field adjustment device includes a shim coil array 20 in which a plurality of shim coils 21 are arranged, a calculation part 23 for determining a current command value of the shim coils 21 based on a unique mode acquired by singular value decomposition of the response matrix from an electric current to a magnetic field of the shim coils 21, and a power source 27 for controlling the electric current of the shim coils 21 based on the determined current command value. One of electric supply lines from the power source 27 to the shim coils 21 is configured so as to be a common electric supply line 30 common to one of electric supply lines to the other shim coils 21.SELECTED DRAWING: Figure 1
