To assemble a rack using panels with the same shape as much as possible, assemble them stably in strength by dispensing with a device such as a driver and prevent screws used for assembling from being detached therefrom to be not lost.

Pairs of storage holes in which knobs of connecting screws are inserted are provided in the left/right in both ends of a panel, respectively, so that when abutting on another panel, the connecting screws are threadedly engaged into internal threads to be connected. The connecting screws are penetratedly provided from the storage holes to the panel end face. The storage holes are formed into long holes in the left/right direction so that the screws can be threaded therein by the operation of the knobs and the screws are so retained as to be prevented from being detached therefrom.