Provided are: a method for producing a molded body that is formed from a fiber-reinforced composite material which has excellent flame retardancy and chemical resistance, while being applicable to complicated shapes; and a multilayer base that is used in this production method. A multilayer base which comprises: at least one prepreg layer containing a resin matrix and a reinforcing fiber sheet; and at least one polymer layer containing a fluorine-containing polymer. This multilayer base is characterized by having at least one interface at which a prepreg layer and a polymer layer are in contact with each other, and is also characterized in that an adhesive functional group is present in the surface of the polymer layer at the interface. A method for producing a molded body, wherein the multilayer base is molded while being heated.