A protective thin-film for a magnetic head is produced by a method comprising vapor-depositing from an atmosphere containing Si, C and H under an operating pressure of less than 0.05 Torr while applying a negative bias voltage of less than -400 V but greater than -1000 V to a magnetic head, a protective thin film on at least the surface of the head facing a recording medium, the protective film containing Si, C and H in amounts of 3-9 at %, 61-81 at % and 16-30 at %, respectively, having a thickness of 1-3 nm and having a refractive index of 2.0 or more.