Abstract: A magnetic shield device is provided wherein an object to be shielded from an ambient field is surrounded by a hollow member of high permeability material which has an opening therein permitting visual or other access to the object but also permitting possible entry of a disturbing portion of the ambient field. A counter magnetic field for opposing and cancelling the disturbing field portion is produced by current flow through a conductor wound around the path of the disturbing field portion, the conductor preferably being in the form of a solenoid coil wound around a tubular portion of the member. A DC current may be applied and/or the conductor may be short-circuited with the current being produced from a counter electromotive force induced from changes in the ambient field.