AUTOMATIC CANCELLER

PROBLEM TO BE SOLVED: To provide an automatic canceller provided with a magnetism sensor that is made small in size and measures precisely the azimuth of magnetic lines of force of the earth magnetism. SOLUTION: The canceller is provided with a cancel coil 5 that applies a cancel magnetic field whose magnetic lines of force are equal in the magnitude and opposite in the direction to those of an external magnetic field to a cathode ray tube 4 and a control section 3 that controls the magnitude of the cancel magnetic field based on the azimuth of the magnetic lines of force by the external magnetic field sensed by a magnetism sensor 2, and the automatic canceller 1 is provided with the magnetism sensor 2 that has a magnetism impedance effect element made of an Fe base soft magnetism metallic glass allay whose major composition is Fe where a temperature interval ΔTx of a supercooled liquid expressed by formula of ΔTx=Tx-Tg, where Tx is a crystallization start temperature and Tg is a glass transition temperature, is >=20 K .