Method for forming multilayer coating film and clear coating used for producing multilayer coating film

A method for forming a multilayer coating film, comprising:

• a step (1) of coating an aqueous first colored coating composition (BC1) onto an object to be coated to form an uncured first colored coating film;
• a step (2) of coating an aqueous one-part type second colored coating composition (BC2) onto the uncured first colored coating film obtained in step (1) to form an uncured second colored coating film;
• a step (3) of coating a clear coating composition (CC) onto the uncured second colored coating film obtained in step (2) to form an uncured clear coating film, wherein
• the clear coating composition (CC) includes a hydroxyl group-containing acrylic resin (A1),
• an isocyanate curing agent (A2), and
• an unsaturated fatty acid ester polyol (D) having at least two hydroxyl groups in one molecule,
• and the distance Ra between the solubility parameters in Hansen space of the hydroxyl group-containing acrylic resin (A1) and the solubility parameters in Hansen space of the unsaturated fatty acid ester polyol (D) is 4.0 or less;
• and
• a step (4) of simultaneously curing the uncured first colored coating film, the uncured second colored coating film, and the uncured clear coating film, formed in steps (1) to (3), by heating at 70 to 100° C.