There is provided a magnetic shield which can shield external magnetic
fields in the direction of an axis of a tubular magnetic shield and in
the direction vertical to the axis. A magnetic shield has a cylindrical
ferromagnetic substance 2-1 having openings on both ends and two
superconducting loops housed in the respective insides of superconducting
loop containers 1-1, 1-2. The superconducting loops are constructed of
high critical temperature superconducting wire. The two superconducting
loops have semicircle shapes and are arranged in x-direction so as to be
symmetrical with respect to an axis of the cylindrical ferromagnetic
substance 2-1. The superconducting loop containers 1-1, 1-2 are arranged
in the insides near both open ends of the cylindrical ferromagnetic
substance 2-1 with supports 20. The superconducting loops are arranged to
be vertical to the axis of the cylindrical ferromagnetic substance 2-1.
The superconducting loops are cooled by liquid nitrogen or a
refrigerator. A lightweight, small magnetic shield having high
operability can be realized.