PURPOSE: To conduct remodeling construction simply by dividing a magnetic shielding device, forming each divided partition in the laminated structure of a magnetic substance sheet and freely changing the number of laminating.

CONSTITUTION: A drum section 203 consists of a plurality of partitions 205 divided in the circumferential direction along the axial direction of a magnet 1, and each partition is shaped in structure in which sheets 206 composed of a magnetic substance are laminated in the radial direction of the magnet. The sheets 206 composed of the magnetic substance are fixed by bolts 208 for fixing mounted to support structures 207. End plates 204 are made of a plurality of partitions 209 radially divided along the radial direction of the magnet 1, and sheets 210 composed of the magnetic substance are laminated and fastened by the bolts 208 for fixing. Accordingly, when a leakage field screening effect must be improved, the sheets 206 and 210 composed of the magnetic substance shaping the drum section 203 and end plates 204 or a magnetic shield 2 are added and laminated at every divided partition 205, 209, and the thickness of the drum section 203 and the end plates 204 is increased, thus simply remodeling a device.