PURPOSE: To effectively use a space of a shelf by forming a flat tray on one surface of a shelf, and forming a holder for holding eggs, bottles, small articles, etc., on the other surface.

CONSTITUTION: When a receiving tray 3 is used as a flat tray part 5, the tray part 5 of the tray 3 is mounted at a front surface side in a rectangular hole 2 of a shelf 1. When the tray 3 is used as an egg holder 6, the tray 3 is removed from the hole 2 of the shelf 1, the tray 3 is so turned over that the holder 6 is moved to a front side, mounted at the hole 2 of the shelf 1, and eggs are placed at circular holes 8 of protrusions 7 of the holder 6 one by one for use. Thus, damage of the egg can be effectively prevented to be preserved in the shelf and the space of the shelf 1 can be effectively used.