PURPOSE: To contrive the increasing of the volume of a box and make it freely handy to carry by making the edges of the two opposite sides of the four sides of the box freely receivable in the groove provided near the edges of the adjacent two opposite sides thereof.

CONSTITUTION: The subject packing box made of foaming resins consists of a bottom part 1, four side parts 21-24 and a top part 3 serving as a lid. The four side parts are connected with the inner surface of the bottom part by sheet-like materials 5 which permit the four side parts to be freely opened and closed and the two opposite side parts are provided at their edges with grooves 6, in which the edges of the other two opposite sides are freely receivable. The two separated pieces of the top part 3 are connected with the top edges of the side parts by the sheet-like materials 5 which permit the top part to be freely opened and closed and the top part including the two separated pieces is freely receivable in the groves 6 provided near the upper edges of the side parts. This method makes the formation and unpacking of the box easy and the placement and removal of various objects possible. Made of foaming resins, this box is solid yet light in weight and also handy to carry.