PURPOSE: To obtain a magnetic thin film provided with high corrosion resistance by a method wherein a wet chromate protective film whose etching amount is 200 or lower is formed on the surface part of an alloy layer composed mainly of Co and/or Fe.

CONSTITUTION: A magnetic thin film is formed by a wet plating method such as an electroplating method or the like. A chromate protective film is formed on the magnetic layer by a wet chromate treatment. The chromate protective film is formed to be a thickness of 100 or lower, the protective film is formed of a required magnetic-pole surface, and no film is formed on the rubbing face of a slider. Since the chromate layer is formed after having melted a CoFe surface slightly, a ball part is set to a recessed state and not damaged by CSS or the like.