To provide a current adjustment method of a demagnetization coil for a vessel capable of increasing a reduction ratio of a far magnetic field as compared with a conventional one and capable of easily performing setting of an energization amount at the vessel.

An energization amount ATO of each M coil is made to the same common value α and a variation degree ΔAt of the energization amount (ST1, ST2) and the energization amount of each M coil is made to α+ΔAT (ST3). Subsequently, a mistake fit degree Mrn of a coil effect degree by the energization amount at this time and a hull magnetic at demagnetization is calculated (ST4). The mistake fit Mrn at this time and the former mistake fit degree Mra are compared with each other (ST5). When Mrn at this time is small, the energization amount of each M coil is increased by ΔAT and new Mrn with the hull magnetic at demagnetization is determined. The processing is repeated until the mistake fit degree Mrn at this time exceeds the former value. When the mistake fit degree Mrn at this time exceeds the former value, ATn at this time is made to an initial value ATf (ST7) and thereafter, it is transferred to individual adjustment of each M coil.