To enable an amount of false products to be accurately acknowledged mainly in reference to their identification Nos. under discrimination for each of the identification Nos. against an external complaint on the packaged product, eliminate necessity for recovering a product not corresponding to the identified one and improve its economic characteristic.

A printing machine 12 prints identification No. of serial number for every region corresponding to one container of a packaging material 10 moving in an arrow indicated direction. A managing computer manages the consecutive identification No. as a memory information. An identification number inspecting machine 20 detects an invalid number of wrong letter from each of said identification numbers. The managing computer may manage it as the memory information. An invalid number excluding means excludes the corresponding packaging material. A packaged item managing means 25 may send information such as weight or temperature of a packaged item to the managing computer. The managing computer may manage the aforesaid information as memory information. Further, a seal managing means 26 may send information such as a seal temperature to the managing computer. The managing computer may manage the above information. Further, the managing computer may manage either a degree of vacuum or an amount of inert gas within the packaging material. The computer may discriminate an error in work for the packaged item, for example, for every identification number under such management as above.