The present invention provides a method for forming a multi-layer coating film by applying a clear coating (B) on the film of a leafing type aluminum flake-containing metallic coating (A), which method comprises forming a film of the metallic coating (A), curing the film, applying thereon a composition (C) containing a polymer formed from an unsaturated monomer having a phosphoric acid group represented by --O--PO(OH)(R.sub.1) (wherein R.sub.1 is a hydroxyl group, a phenyl group or a C.sub.1-20 alkyl group) and a hydroxyl group-containing unsaturated monomer, and then applying the clear coating (B) on the film of the composition (C). The method can form a multi-layer coating film improved in interlayer adhesivity between the metallic coating film and the clear coating film, without reducing the excellent effects and metallic feeling provided by a metallic coating film containing leafing type aluminum flake.