To obtain a superior frequency characteristic, and miniaturize and thin in both analog and digital frequency bands.

A magnetic material constituting a pulse transformer magnetic core 1, capable of being used in both frequency bands of an analog signal and digital signal has permeability 50,000 or over at 100 Hz and permeability 100 or over at 10 MHz. The magnetic material is in particular not limited is long is at contains such permeabilities, but in particular preferably is composed of an amorphous alloy, preferably a Co system amorphous alloy. Furthermore, a magnetic core or magnetic thin band is heated in a magnetic field. Intensity of the applied magnetic field is set to 1 Oe or higher. It is sufficient that thermal processing temperatures be the Curie temperature or lower, and preferably are set to 180°C or higher. Furthermore, the thickness of a magnetic thin band is preferably 30 μm or less.