To provide an assembled structure made of plastic which promises an easy attachment of a shelf board and a back board to an exterior body.

The exterior body for a box with shelves is composed by a pair of side boards 3, 3 and a top plate 4. The back board 6 is joined to the shelf board 5 integrally through a thin hinge 7. The shelf board 5 is attached between a pair of the side boards 3, 3, and the back board 6 is attached between a pair of the side boards 3, 3 by bending the hinge 7. Supporting shafts 9 are provided at the both ends of the shelf board 5 and at the both ends of the back board 6 respectively. The structure to attach the shelf board 5 and the back board 6 to the pair of the side boards 3, 3 are obtained by forming recessed parts 10 at places on a pair of the side boards 3, 3 where the supporting shafts 9 on the shelf board 5 and the back board 6 correspond.