Abstract: A method of forming trim cover being one of elements constituting a seat which is used for furniture or as an automobile seat, comprises feeding an assembly of a sheet of covering material and wadding material, with the covering sheet side of the assembly turned upward, onto support means for receiving and supporting the assembly thereon. The support means has at least one hole of a desired predetermined shape. A portion of the assembly substantially positionally corresponding to at least one hole is pressed downwardly to cause a portion of the wadding material of the assembly positionally corresponding to the hole of the support means to be protruded downwardly from the support means through the hole of the support means. The protruded portion of the wading material of the assembly is cut, while the same portion of the assembly is still pressed downwardly. The assembly is advanced to a backing sheet laminating station.