PURPOSE: To provide an outer coating contrived in the maintenance of moisture resistance at high temperatures and in the prevention of the high elasticity of outer coated products, and improved in its production efficiency.

CONSTITUTION: A filler containing a thermoplastic resin (e.g. polyethylene) as a filler component is added to a thermosetting resin. Polyethylene having an average mol.wt. of 1500-3000, a density of 0.90-0.99g/cm3, an average particle diameter of 20-40μm and a melting point of approximately 110-140°C is employed as the above-mentioned polyethylene preferably in an amount of 5-20wt.%. By the addition of the thermoplastic resin, cavities formed on the curing of the thermosetting resin are filled up with the thermoplastic resin to reduce the pore degree of the coated product, thereby largely improving the moisture resistance of the coated product.