Abstract: The invention relates to an on-track maintenance machine for maintaining a superstructure with a track panel formed of sleepers and rails fixed thereon that is supported on a ballast bed, comprising a lifting and lining unit for track lifting and lining and a tamping unit for track tamping. In the invention, at least one rail treatment unit for continuous reprofiling of the rails is arranged on a machine frame. The elimination of rail defects contributes to a higher durability of the corrected track position, as after re-opening the treated track section, the rails can be used again trouble-free.