To provide a packaging box which can be highly operatively assembled, has relatively little part to be pasted and is excellent in lightproofness although it has an approximately similar structure to that of a conventional packaging box.

The packaging box consists of a body box 3 and a lid box 5. The body box 3 consists of an inner box 7 and an outer box 9 whose developments are connected via an acute-angled crease, and four flaps F1 to F4 provided on the outer box 9. The developments of the inner box 7 and the outer box 9 are continuously structured, so that the inner box 7 and the outer box 9 can be formed sequentially by rolling both developments. A lid fitting part 13 protruding upward from the upper end of the outer box 9 is formed on the upper end of the inner box 7, and the lid box 5 is fitted therein. A lightproof auxiliary flap F9 is also connected to the lower side of one of plates constituting the inner box 7.