To obtain a coating material composition capable of affording a precoated steel plate excellent in resistance to corrosion, acid and boiling water and in processibility without using a chromate rustproof pigment.

The objective coating material composition comprises film- forming resin components comprising (A) 20-90 pts.wt. of a hydroxyl group- containing polyester resin having a glass transition temperature of 10-100°C and a number average mol.wt. of 2,000-25,000, (B) 5-70 pts.wt. of a novolak type epoxy resin and (C) 5-40 pts.wt. of at least one curing agent selected from amino resins and blocked polyisocyanates, and (D) 30-100 pts.wt., based on 100 pts.wt. of the total of the film forming resin components, of calcium ion- exchanged amorphous silica particulates. This coating material composition forms a cured coating film having a glass transition temperature of 40-80°C. The coated steel plates are obtained by forming an undercoating from the above coating material composition on various steel plates and then forming thereon an overcoating film having a glass transition temperature of 20-80°C.