The arm of the invention (1) for operating the roller planes (31) of a storage unit (30) for stocking ceramic products comprises: a main longitudinal member provided with a plurality of organs (4) for operating the ends of rollers (31) of each plane of the storage unit (30); a supporting longitudinal member, to which the main longitudinal member is hinged, activated vertically with stepped motion and activated horizontally to allow the operating organs (4) to engage/disengage with or from the ends of the rollers (31) of each plane of the storage unit (30).