To provide a reinforcing device for an on-desk shelf with high strength in connection between both sideboards though a degree of freedom relative to storage bodies attachment position in an inner space concerning the on-desk shelf which has a basic structure with a rear board connected between the rear ends of both the sideboards and where storage bodies such as book stands or shelf boards are freely removably changed in the vertical and horizontal attachment positions in the inner space with an open front which is formed with both the sideboards and the rear board.

The storage bodies such as the book stands 5 or the shelf boards are freely removably changed in the vertical and horizontal attachment positions in the inner space with the open front, which is formed with both the sideboards 3 and the rear board 4, without arranging any members for connecting both the sideboards concerning the on-desk shelf to be placed on the rear part of the top plate of a learning desk. The rear board is connected between the rear part of both the sideboards and also the position of the rear surface of the rear board is set to be arranged a little near to a front part from the rear ends of both the sideboards. Then, a reinforcing member 40A is connected to a part between at least inner side surfaces of the rear projections 3A on the sideboards.