A processing method for molding a foamed polymer, which includes molding a mixture of a polymer material and a foaming agent in a space of a mould chamber into a molded article having a predetermined shape. The shape of the entire space of the mould chamber is an injection molding shape that is different from the shape of the molded article before the mould chamber is fully filled with the mixture, and a shape of at least one local part of the mould chamber is changed after the space of the mould chamber is fully filled with the mixture. An exterior peripheral surface of a substrate of a movable portion and an adjustment end face are located in a center portion of a first mould surface and are spaced apart from all outer edges of the first mould surface.