Abstract: The invention relates to a chemical mechanical polishing system, comprising: at least one polishing platens rotatably installed with a platen pad mounted on its upper surface; a guide rail disposed along a predetermined path; a substrate carrier unit including a rotary union to downwardly press a substrate during a polishing process, the substrate carrier unit moving along the guide rail with loading the substrate; and a docking unit installed to be docked to the substrate carrier unit so as to supply air pressure to the rotary union which downwardly presses the substrate held by the substrate carrier unit, when the substrate carrier unit is positioned over the polishing platen, whereby even though the substrate carrier unit is moved to consecutively polish the substrate on the plural polishing platens, it substantially removes a phenomenon of the twisting of air pressure supply tubes due to the movement of the substrate carrier unit.