Abstract: A joining device, particularly for joining a shelf to a wall of a piece of furniture, includes a cylindrical body that can be associated in a first hole adapted to be provided transversely in the shelf and provided with a first axial seat for the rotatable coupling of the first stem of a screw provided with a first crown-shaped head that can be arranged rotatably within a second seat that is adjacent to the first seat. The cylindrical body is provided with a third seat, which is perpendicular and connected to the second seat, for the temporary coupling of a pinion, which interacts with the first crown-shaped head, which protrudes externally to the cylindrical body and is accommodated within a second hole.