To provide a packaging box which reduces a packaging material cost, and allows the visual recognition of a part of a stored article from the outside or exposure of the stored article.

The packaging box of a wrap-round style is made out of a sheet of paper blank, which includes a front board, a bottom board, a back board, a top board, an adhesive strip, which are connected laterally via folding lines, inner flaps connected to both left/right ends of the front board and of the back board via folding lines, and outer flaps connected to both left/right ends of the bottom board and of the top board via folding lines. The length of the inner flaps connected to both left/right ends of the front board and the back board and the length of the outer flaps connected to both left/right ends of the bottom board and the top board are so determined as to form rectangular openings of a given size on the left/right side faces of the box, respectively. The paper blank further has zipper portions each formed at a given position in the front board and in the back board in such a way that the zipper portions extend to reach the edges of the connected inner flaps across the left/right edges of the front board and back board to be counter to each other and that a series of incision lines are formed linearly to allows continuous breaking of the zipper portions. The front board is glued to the adhesive board to assemble the packaging box.