To prevent appearance of a corrugated fiberboard box from degrading even if a seal tape is peeled off and allow the box to be repetitively used by pasting a protective adhesive tape to parts of an upper lid flap and opposite side plates where the seal adhesive tape is pasted.

In a corrugated fiberboard box 1 for packing by folding first upper lid flaps 7 and second upper lid flaps 8 in this sequence toward a corrugated fiberboard box body 2, while the second upper lid flaps 8, 8 float from the first upper lid flaps 7, 7, a protective tape 11 is pasted along a butted parts of the second upper lid flaps 8, 8. Further, a part of the protective adhesive tape 11 is pushed into a slit 9 to be pasted to rear faces of ends of the second upper lid flaps 8, 8 and to ends of surfaces of the first upper lid flaps 7, 7, and also an end of the protective tape 11 led from the slit 9 is pasted also to upper surfaces of opposite short side plates 3, 3. Then respective butted parts and folds pushed into the slit 9 are cut to have the box freely opened/ closed.