PURPOSE: To simplify transportation and to ease assembling work by adopting the structure in which the bottom-plate unit and the side-board unit of a cargo case can be joined with bolts into an integrated part.

CONSTITUTION: To combine a cargo case bottom-plate unit A with a cargo case side-board unit B, at first the upper installing surface 11 on the side board 6 side is abutted to a lower installing surface 5 on the bottom-plate side 1, next both upper and lower installing holes 14 and 16 are brought into accord with each other, and then a horizontal surface 13 of a connecting part 10 is abutted to the bottom surface of a cross-member 3. After this, a fixing bolt 17 is inserted from underneath the bottom plate 1 so that the bolt 17 gets through both the lower and upper installing holes 16 and 14 and is screwed with a nut 15. Thus, the unit A and B are combined. At the completion of joining by the fixing bolt 17, the abutting part between the horizontal surface 13 and the double-cross member 3 is welded.