To provide a method for producing a formed product comprising a fiber-reinforced composite material which is excellent in flame retardancy and chemical resistance and which can be formed into a complicated shape; and a laminated substrate which is used for the production method. A laminated substrate comprising at least one prepreg layer containing a reinforcing fiber sheet and a resin matrix, and at least one polymer layer containing a fluorinated polymer, wherein at least one interface where the prepreg layer and the polymer layer are in contact with each other is present, and adhesive functional groups are present in the surface of the polymer layer at the interface; and a method for producing a formed product, which comprises forming the above laminated substrate with heating.