PURPOSE: To improve the space factor and scratching resistance by coating a paint contg. a radical polymerizable or cation polymerizable resin on a ferrous or cobalt amorphous alloy surface then irradiating electron rays or UV rays thereon to cure the coating.

CONSTITUTION: The paint contg. the radical polymerizable or cation polymerizable resin (e.g., 20% toluene soln. essentially consisting of a trifunctional acrylate monomer and 20% MIBK soln. essentially consisting of a bifunctional alicyclic epoxy resin) is coated on the ferrous or cobalt amorphous alloy surface and thereafter, the electron rays or UV rays are irradiated thereon to cure the coating. As a result, the insulating film for the amorphous alloy having a large space factor, hence large inter-layer resistance value and excellent scratching resistance is thus formed.