PURPOSE: To form a bottomed receiving part receiving a flat plate-shaped article such as an optical disk to the surface of a substrate made of corrugated cardboard.

CONSTITUTION: The slit having depth cutting one patch paper and core paper so as to leave the other patch paper is applied to one side surface of a substrate A made of corrugated cardboard consisting of core paper having a corrugated cross section and the patch papers bonded to both surfaces of the core paper in the shape almost same to the contour of a flat plate-shaped article and the substrate part surrounded by the slit is pressed to the remaining patch paper to collapse and flatten the core paper to form a receiving part B having the depressed bottom C due to the substrate part.