PURPOSE: To make a magnetostatic field generation coil adjustable in the position and free from effect of a magnetostatic field generated on a mounting attitude or the like thereof, by grasping the magnetostatic field generation coil from four directions, the external circumference, both sides and internal circumference thereof.
CONSTITUTION: Circular magnetostatic field generation coils 11 mounted respectively at the center of an armor case 10 and on the concentric circle thereof are so arranged on the armor case with fittings to be adjustable in the position. A magnetostatic field generation coil fixing section 22 grasps both sides of the magnetostatic field coil 11 between side contact members 20 while doing the external circumference and the internal circumference thereof 11 between an external circumference contact member 19 and an internal circumference contact member 21. The positional adjustment of the magnetostatic field generation coil is performed by turning heads 15a of three support bolts 15 with a spanner or the like. A notch 13 herein provided helps the spanner to engage the support bolts, thereby facilitating the turning thereof.