PURPOSE: To prevent the deviation of thickness of a winding material by a method in which a heat-meltable resin band of a small width is bonded to a sheet material, and the sheet material is wound up while rolling a thick deviation- correcting sheet into the sheet portion other than the bonded portion.

CONSTITUTION: A sheet material 10 is fed by rolls 12W15 provided between drums 11 and 16, and adhesive aids 19A and 19B are coated on one edge of the sheet material 10 by coaters 17 and 18. A small width band 21 of heat-meltable resin is pressingly coated on the coating portion of the material 10 between rolls 14 and 15. The coating portion is dried and preheated by a heater 20 and then cooled by a cooler 23 after press bonding. The bonded sheet material 10 is wound around a drum 16 while rolling a thick deviation-correcting sheet 31 into the sheet portion other than the bonded portion of the small width band 21. The deviation of the thickness of the sheet material so wound can thus be prevented.