To provide a polishing apparatus for electrolytic-polishing the inner surface of a predetermined principal part of the inner surface of a straight part or a bent part of a transport pipe with high accuracy.

This polishing apparatus includes: an electrolyte polishing device composed of a magnetic substance universal nozzle passed through the transport pipe and connecting an inner pipe tractor and an electrolyte supply pipe, a pair of soft umbrella-like shields disposed opposite to each other in front and at the back of the magnetic substance nozzle, and a stopper for releasing the closed state of the paired soft umbrella-like shields; an a repulsive magnetic field forming device composed of a mounting fixed body removably provided on the outer periphery of an object to be polished of the transport pipe; a rotary pulley, an internal ring gear and a sun gear provided on the mounting fixed body; a plurality of planetary gears meshing between the internal ring gear and the sun gear; and a magnet disc fixed to the rotating shaft of the planetary gear and revolving and rotating on its axis with the planetary gear.