Abstract: Provided is a method for forming a multi-layer coating film which makes it possible to form a multi-layer coating film which exhibits excellent smoothness and luster. The present invention forms, on a cured electrodeposited coating film formed on a stell plate, a first colored coating film comprising a first coloring coating material (P1), a second coating film comprising a second aqueous coating material (P2) having specific viscometric properties, a third colored coating film comprising a third aqueous color coating material (P3) which has a specific coating material solid content concentration (NVP3) and contains a lustrous pigment (BP3), and a clearcoat film comprising a clearcoat material (P4). The present invention simultaneously cures the formed multi-layer coating film by heating.