When a laminated gasket product is demolded from a mold in production thereof by a conventional production process, the gasket product is rubbed against the mold and, therefore, minute scratches are formed on a surface of the gasket product. The minute scratches may impair the reliable sealability of a liquid drug. A method for producing a gasket (13) for use in a prefilled syringe (10) includes the steps of: preparing a gasket forming mold； molding a gasket (13) in the mold, the gasket having a surface laminated with a lamination film (15) and including a circumferential surface portion (17)； demolding the gasket (13) from the mold, and then simultaneously forming a groove (22) and a projection (24) each extending circumferentially of the gasket in a portion of the lamination film (15) present in the circumferential surface portion (17) of the gasket.
