To provide a service condition as desired by supporting shelves in horizontal or inclined positions.

A shelf 4 is supported between right and left support frames 2 by an engagement means comprising hooks 24 provided at the four corners of the shelf and locking holes 19, 20, in such a way that it can be removed and that its height can be adjusted. The engagement means is designed to be capable of engaging the shelf 4 in its horizontal and inclined positions. The shelf 4 can be supported, not only in its horizontal position but also in its inclined position, between the right and left support frames 2 via engagement between the hooks 24 and the locking holes 19, 20 of the engagement means.