Abstract: A method of producing an outer cushion layer for a seatback is disclosed, which comprises preparing a base cushion layer material which is of a flexible layered structure, stamping out a shaped cushion material from the base cushion layer material, the shaped cushion layer material being of a train of cushion pieces which are connected to one another through integrally connecting bridge portions, bringing mutually facing edge portions of every adjacent two of the cushion pieces into contact with each other having the integrally connecting bridge portions protruded from one side of the shaped cushion material, and stitching the protruded portions and the mutually contacting edge portions of the shaped cushion layer material. With this method, an outer cushion layer having a smoothly corrugated surface is produced.