The present invention provides a multilayer coating film-forming method that is capable of forming a multilayer coating film with excellent finished appearance and excellent luster. The aqueous base paint (X) is applied by using a rotary-atomization bell-shaped coater under coating conditions of a shaping air pressure of 0.15 to 0.25 MPa and a paint discharge amount of 100 to 300 cm3/min. The viscosity 60 seconds after the application of the aqueous base paint (X), measured at a temperature of 23° C. and a shear rate of 0.1 sec-1, is 90 to 160 Pa·s, the solids content 60 seconds after the application is 20 to 40 mass %, and the film thickness 60 seconds after the application is 17 to 35 μm. The effect pigment dispersion (Y) contains a flake-aluminum pigment (A) with an average thickness of 1 nm or more and less than 70 nm, a flake-aluminum pigment (B) with an average thickness of 70 nm to 250 nm, a hydroxy-containing acrylic resin (C), a rheology control agent (D), a surface-adjusting agent (E), and water, the effect pigment dispersion (Y) having a solids content of 2 to 9 mass %. The effect coating film after curing has a film thickness of 0.5 to 2.0 μm.