PURPOSE: To avoid adhesion of unnecessary substances which disturb a static magnetic field generated by permanent magnets by a method wherein magnetic shielding members made of nonmagnetic material are attached to a yoke so as to cover the main flux generating surfaces of the permanent magnets and to be detached easily.

CONSTITUTION: A magnetic resonance device is composed of an approximately square yoke 5 made of pure iron, static magnetic field generating means which are composed of permanent magnets 6 and poles 7 made of magnetic material and are attached to the lower side center and the upper side center of the upper yoke member 5a and the lower yoke member 5b of the yoke members forming the yoke 5 respectively so as to face each other and magnetic shielding members 9 made of nonmagnetic material which cover the main flux generating surfaces 11 of the static magnetic field generating means and are attached to the yoke 5 with bolts 10 at their both ends. The magnetic shielding member 9 has approximately U-shape as a whole and has a protruding part which corresponds to a recessed part formed on the surface of the corresponding pole 7 at its center and has bolt holes 13 through which the shielding member 9 is fixed to standing yoke members 5c and 5c by bolts 10 so as to be attached and detached freely at its both leg parts 9a and 9a.