To form by folding and sticking required portions of a single sheet base material and to include sufficient cushioning function by reinforcing fitted portions of a product by right and left rectangular portions, an overlap between a side rest and a reinforcing plate and an internal base wall.

A sheet base material is folded at respective creases in required orientations, and a fixing plate 13 is stuck to a rear surface wall 14, an overlap plate 17 is stuck to an internal placing plate 12, and a reinforcing plate 23 is stuck to a side rest 20 respectively via an adhesive. In addition, the side rest 20, a support plate 22 and the reinforcing plate 23 are folded in required orientations at creases to form a paper cushion A. In addition, right and left rectangular portions 33 surrounded by both right and left ends of a front end wall 11, both right and left ends of a base wall 10, the side rest 20, the support plate 22 and the reinforcing plate are formed, and the rectangular portion 33, an overlap between the side rest 20 and the reinforcing plate 23 and an internal base wall 28 are used to reinforce fitted portions of a product. Thus cushioning function can be largely improved.