Abstract: A method for forming a multi-layer coating film by forming an undercoating film, a glittering material-containing base coating film and a clear coating film in this order on a substrate to be coated, in which a glittering material-containing base coating material for forming the glittering material-containing base coating film contains colloid particles containing a noble metal and/or a metal and a coating film-forming resin, and the undercoating film has a hue in a range of from +35 to +50 and ?35 to ?50 on a Munsell 100-hue ring with counterclockwise rotation on the hue ring being represented by from 0 to +50 and clockwise rotation being represented by from 0 to ?50 where a hue of plasmon coloration of the colloid particles containing a noble metal and/or a metal is 0 on the hue ring, and has a brightness of 9 or less on a Munsell color system, or the undercoating film has an achromatic color having a brightness of 4 or less on a Munsell color system.