To ensure appearance of a vehicle sheet by thinning a trim cover sewing portion, by removing a groove for embedding the sewing portion from a sheet pad, and by using not only a thick and stiff skin material, such as natural leather and synthetic leather, but also a thick and dense wadding material.

In two trim cover materials 12, 12, the wadding material is removed to remain as margins to seam 20, 20 within prescribed ranges 19, 19 of terminals 18, 18 of the respective skin materials 15, 15, and the wadding materials 23, 23 are integrally stacked onto rears 17, 17 of the skin materials 15, 15. Then, fronts 16, 16 of the skin materials 15, 15 are overlapped mutually to sew the margins of seam 20, 20 at a position alienated from terminals 24, 24 of the wadding materials 23, 23 by prescribed spacing. Successively, the wadding materials 15, 15 are folded over, and terminals 21, 21 of the margins of seam 20, 20 are folded over and bent corresponding to the rears 17, 17 of the skin materials 15, 15, thus forming a sewing portion 22, where no wadding materials 23, 23 exist.