A method for forming a multilayer coating film, sequentially conducting step (1) of applying an aqueous 2-package type first colored paint on both a metal member and a plastic member of an automobile outer panel to form an uncured first colored coating film; step (2) of applying an aqueous 1-package type white paint on the uncured first colored coating film by step (1) to form an uncured white coating film; step (3) of applying an aqueous 1-package type interference color paint on the uncured white coating film by step (2) to form an uncured interference color coating film; step (4) of applying a solvent-based 2-package type clear paint on the uncured interference color coating film by step (3) to form an uncured clear coating film; and step (5) of heating these coating films by steps (1) to (4) at 75 to 100° C. to simultaneously cure them.