An object of the present invention is to provide a coating composition for forming a coating film having extremely high scratch resistance which could not be achieved up to now, concretely, such a degree of scratch resistance that even if the surface of a coating film is rubbed under strong external force by a cloud of sand flying and others while car washing and running, the surface can endure it. As a means of achieving this object, the coating composition according to the present invention comprises acrylic resin (A) having a short side chain hydroxyl group (a1) and a long side chain hydroxyl group (a2) and polyisocyanate prepolymer (C) as essential components and, as the need arises, further comprises polylactonepolyol (B), wherein the content ratio of the short side chain hydroxyl group (a1) to the long side chain hydroxyl group (a2), the total hydroxyl value of the short side chain hydroxyl group (a1) and the long side chain hydroxyl group (a2), the solid content ratio of the acrylic resin (A) to the polylactonepolyol (B), and the amount of the polyisocyanate prepolymer (C) being combined are in their respective specific ranges.