This invention offers a method for forming multilayer coating film by successively applying onto a coating object a water-based first coloring paint, water-based second coloring paint and clear paint, and simultaneously baking the resultant first coloring coating film, second coloring coating film and clear coating film, in which the water-based first coloring paint (A) comprises polyester resin and curing agent, the polyester resin containing benzene ring and cyclohexane ring in its molecules, their combined content in the polyester resin being within a range of 1.0-2.2 mols/kg (solid resin content); and that the curing agent is at least one compound selected from the group consisting of isocyanate group-containing compound, oxazoline group-containing compound, carbodiimide group-containing compound, hydrazide group-containing compound and semicarbazide group-containing compound. According to this method, multilayer coating film excelling in smoothness, distinctness of image, chipping resistance and water resistance can be formed by 3-coat-1-bake system.