sorting unit for belt conveyor plants , of the type comprising a first sorting conveyor belt extending between first transmission rollers and revolvingly oscillating around a first oscillation axis , extending in parallel and close to one of its longitudinal edges . a second sorting belt is also provided , which extends between second transmission rollers and is placed aside the first sorting belt at the opposite side to the first oscillation axis , as well as revolvingly oscillating around a second oscillation axis running in parallel and in correspondence of its longitudinal edge placed at the opposite side with respect to the first sorting belt .