A coating composition useful for improving the surface properties, such as surface hardness and chemical resistance, of plastic products, wooden products, metallic products, or the like, which comprises (A) silicon compounds partial hydrolyzates comprising a partial hydrolyzate of a tetraalkoxysilane and a partial hydrolyzate of an organic silicon compound of the formula: R.sub.n Si(OR').sub.4.sub.-n wherein R is a hydrocarbon group, R' is an alkyl and n is 1 or 2, and (B) an acrylic copolymer and an etherated methylolmelamine, which are dissolved in a solvent. The coating composition can give a transparent coating film having excellent hardness, water resistance, boiling water resistance, chemical resistance, heat cycle resistance and weatherability, and further antistatic properties onto the formed products.