To decide piling position of open boxes to minimize frequency in generation in quality defect.

This device for optimally piling open boxes has an intellectual database 20, a delivery order file 100, a delivery parts shape information database 200, a package specification database 300, a delivery management database 400, a quality check information database 500, a carrying module piling position information database 600, a box information database 700 and an unpacking base side terminal 800. When a quality defect is generated, search in the intellectual database 20 is performed to select an open box having the same volume with the open box, wherein the defect is generated, or a combination of the open boxes. The open box having the lowest frequency in generation of defect among the selected open boxes or combination thereof is replaced in the piling position of the open box, wherein the defect is generated, to reduce the defect generation ratio.