To provide a structure for mounting a back panel in a built-up rack which allows freely selecting the longitudinal mounting position of the back panel without a gap forming between the back panel and each side face member, and which allows easy mounting and removal.

This built-up rack has a table board 5 mounted between a pair of right and left side face members 2 and 2. A pair of right and left back panel brackets 31 each formed with a forwardly-faced locking hook at a loose end spaced from the inner surface of each of the opposite side face members 2, 2 are mounted on the inner surfaces of the opposite side face members 2, 2 and a back panel 6 having about the same width as the inner surface of the side face member 2 opposite thereto and having both right and left end edges bent backward into U-shaped cross sections, with locking holes board in these bent parts to correspond to the forwardly faced locking hooks, is locked to the back panel brackets 31.