Method for forming multi-layered coating film

A method for forming a multilayer coating film by sequentially performing the following steps (1) to (4):

• (1) applying an aqueous first colored coating composition (X) comprising a film-forming resin (A) and a pigment (B) to a substrate to form an uncured first colored coating film,
• the film-forming resin (A) comprising a hydroxy-containing polyester resin (A1), the hydroxy-containing polyester resin (A1) having an acid value of 30 mg KOH/g or less;
• (2) applying an aqueous second colored coating composition (Y) comprising a film-forming resin (C) and a copolymer (D) to the uncured colored coating film obtained in step (1) to form an uncured second colored coating film,
• the copolymer (D) being obtainable by copolymerizing monomer component (d) comprising a macromonomer (d1) and a polymerizable unsaturated monomer (d2),
• the macromonomer (d1) having a polymerizable unsaturated group and a backbone that comprises a polymer chain having a number average molecular weight of 1,000 to 10,000, the macromonomer (d1) being obtainable by polymerizing monomer component (m) comprising 5 to 100 mass % of a polymerizable unsaturated monomer (m1), the polymerizable unsaturated monomer (m1) containing a C4-24 alkyl group;
• the polymerizable unsaturated monomer (d2) having a hydrophilic group;
• (3) applying a clear coating composition (Z) to the uncured second colored coating film obtained in step (2) to form an uncured clear coating film;
• and
• (4) heating the uncured first colored coating film, the uncured second colored coating film, and the uncured clear coating film formed respectively in steps (1) to (3) to simultaneously cure these three coating films.