This invention provides a water-based paint composition comprising an emulsion resin (A), melamine resin (B) and hydrophobic solvent (C), the emulsion resin (A) being fine resin particles having core/shell type multilayered structure composed of the core made of a copolymer (I) obtained by copolymerization of 0.1-30 mass % of polymerizable unsaturated monomer (a) having at least two polymerizable unsaturated groups per molecule and 70-99.9 mass % of other polymerizable unsaturated monomer (b), and the shell made of a copolymer (II) obtained by copolymerization of 5-50 mass % of vinyl aromatic compound (c) and 50-95 mass % of other polymerizable unsaturated monomer (d), the solid mass ratio of the copolymer (I)/copolymer (II) being within a range of 10/90-90/10; the melamine resin (B) having a weight-average molecular weight within a range of 1,000-5,000; and containing, per 100 mass parts of solid resin content in the water-based paint composition, the emulsion resin (A) within a range of 10-80 mass parts, the melamine resin (B), within a range of 5-50 mass parts, and the hydrophobic solvent (C), within a range of 10-100 mass parts. Use of the water-based paint composition allows formation of coating film free of metallic mottling and excelling in flip-flop property, smoothness, luster and water resistance.