Provided is a method for forming a multilayer coating film, said method being suitably applicable to a wet-on-wet coating process comprising: applying a first water-borne base coating material to form an uncured first water-based base coating; and then applying a second water-based base coating material without preheating the uncured first water-borne base coating. A method for forming a multilayer coating film according to a wet-on-wet coating process which comprises applying a first water-based base coating material to the surface of a substrate to be coated and then applying, without preheating the thus formed coating, a second water-based base coating material, characterized in that: the first water-borne base coating material contains a hydrophilic association-type viscous material; and the composition of the second water-based base coating material is controlled.