To surely prevent a round shelf board and shelf board brackets from playing in a horizontal direction and to prevent the rising of the rear part of the round shelf board though a load is concentrated to thee front part of the round shelf board.

Outward pawls 17 are formed at the upper part of the inner end of respective front and back shelf board brackets 13; upward pawls 16 are formed at outer end parts; and an outer part reinforcing member 21 facing a front and back direction forming a pair of front/rear downward projections 24 and an inner part reinforcing member 22 facing the front/back direction forming a pair of pair of front and rear fitting holes 23 to the inner side surface are fixed to the lower surface of the round shelf board 9. Then, the pawls 17 are fitted into the fitting holes 23 of the member 22; the pawls 16 of the brackets 13 are abutted on the outer edge of the member 21; the vertical pieces of the brackets 13 are abutted on the projections 24.