PURPOSE: To manufacture the titled box efficiently by a method wherein a base with a decorative sheet is cut in a specific way, bent, stuck and the cover plate with a decolative sheet is attached to the opening of a square tube obtained.

CONSTITUTION: (1) After the decorative sheet 2 is stuck as if the rectangular base plate 1 is wrapped, the base plate 1 is cut as indicated by a dotted line (a) to provide the 1st inclined surface 3 while the base plate 1 is cut as incidated by dotted lines (b, c) to provide the 2nd inclined surfaces 4, 4'. (2) After three V-grooves 5 are provided at an intended distance, (3) The base plate 1 cut is bent through these V-grooves 5 and stuck through adhesive agent to provide a square tube body 6. (4) A cover plate 7, in which the sides are cut to the angle fitting to the above-mentioned 1st inclined surfaces 3 and decorative sheets 2' are attached to the upper and lower surfaces, are attached and fixed to the opening part of the above-mentioned square tube body 6 to provide a desired closed box.