A water-based coating composition to be used as a water-based first pigmented coating material in a multilayer coating film-forming method in which the following steps to are carried out in order: step: a step of coating an article to be coated with a water-based first pigmented coating material to form a first pigmented coating film, step: a step of coating the uncured first pigmented coating film formed in step with a water-based second pigmented coating material to form a second pigmented coating film, step: a step of coating the uncured second pigmented coating film formed in step with a clear coating material to form a clear coating film, and step: a step of bake curing the multilayer coating film formed in steps to, wherein: the water-based coating composition comprises 7 to 60 mass% of an acrylic resin emulsion (a), 10 to 60 mass% of a coating film-forming resin (b) and 10 to 50 mass% of a curing agent (c), based on the total mass of the solid resin content in the water-based coating composition, the acrylic resin emulsion (a) has a core-shell structure, the core section comprising, as a copolymerizing component, 0.1 to 10 mass% of a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in the molecule, based on the total mass of the monomers of the core section, and the shell section comprising, as a copolymerizing component, a hydroxyl group-containing polymerizable unsaturated monomer, the hydroxyl value of the core section is 50 to 200 mgKOH/g and the hydroxyl value of the shell section is 50 to 200 mgKOH/g, and the coating film-forming resin (b) comprises at least one type selected from among polyester resins, water-soluble acrylic resins and urethane resins. a step of bake curing the multilayer coating film formed in steps to, wherein: the water-based coating composition comprises 7 to 60 mass% of an acrylic resin emulsion (a), 10 to 60 mass% of a coating film-forming resin (b) and 10 to 50 mass% of a curing agent (c), based on the total mass of the solid resin content in the water-based coating composition, the acrylic resin emulsion (a) has a core-shell structure, the core section comprising, as a copolymerizing component, 0.1 to 10 mass% of a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in the molecule, based on the total mass of the monomers of the core section, and the shell section comprising, as a copolymerizing component, a hydroxyl group-containing polymerizable unsaturated monomer, the hydroxyl value of the core section is 50 to 200 mgKOH/g and the hydroxyl value of the shell section is 50 to 200 mgKOH/g, the water-based coating composition comprises 7 to 60 mass% of an acrylic resin emulsion (a), 10 to 60 mass% of a coating film-forming resin (b) and 10 to 50 mass% of a curing agent (c), based on the total mass of the solid resin content in the water-based coating composition, the acrylic resin emulsion (a) has a core-shell structure, the core section comprising, as a copolymerizing component, 0.1 to 10 mass% of a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in the molecule, based on the total mass of the monomers of the core section, and the shell section comprising, as a copolymerizing component, a hydroxyl group-containing polymerizable unsaturated monomer, the hydroxyl value of the core section is 50 to 200 mgKOH/g and the hydroxyl value of the shell section is 50 to 200 mgKOH/g, and the coating film-forming resin (b) comprises at least one type selected from among polyester resins, water-soluble acrylic resins and urethane resins.