An accordion-structured welded bellows for a semiconductor-manufacturing device is characterized in that a plurality of annular bellows plates having curved surfaces in a radial direction are connected in an alternating fashion on the outside-diameter side and the inside-diameter side, wherein the annular bellows plates have a processing-side bellows plate and a non-processing-side bellows plate, a gas layer is interposed between the two bellows plates, the processing-side bellows plate is configured as a thick plate, and the non-processing-side bellows plate is configured as a thin plate. The welded bellows is less likely to be damaged by foreign matter and to be able to use the non-processing-side bellows plate to compensate for any damage to the processing-side bellows plate.