To enable a stored item within a box to be easily confirmed or checked.

This cardboard is constructed to have an opening portion formed while a transparent or translucent synthetic resin film is adhered to side surfaces of a box. This arrangement as above facilitates confirmation or check of an inner part of the box. It becomes possible to perform discrimination and arrangement for facilitating either a classification or discrimination of cargos by applying several colors at the cardboard and the packaged box.