The present invention aims to provide a method for forming a multilayer coating film having good coating film smoothness. A method for forming a multilayer coating film, comprising a first aqueous coating composition application step of applying a first aqueous coating composition (A) to form an uncured first aqueous coating film; a second aqueous coating composition application step of applying a second aqueous coating composition (B) onto the uncured first aqueous coating film to form an uncured second aqueous coating film; a clear coating step of applying a clear coating composition (C) onto the uncured second aqueous coating film to form an uncured clear coating film; and a curing step of heat-curing at once these coating films to form a multilayer coating film, wherein the first aqueous coating composition (A) contains a water-dispersible polyurethane resin (a1) and a viscosity modifier (a2), and the second aqueous coating composition (B) contains water and an organic solvent as diluent components besides solid matters in a state of dilution to a coating viscosity.