To provide a polishing device and method improving the efficiency for polishing and flattening a TFT (thin film transistor) substrate.

This polishing device reduces the time required for lowering by lowering a polishing head at a speed Vh higher than a speed V1 while the height position of a polishing surface is from an initial height H0 to a change height Hc and by lowering the polishing head at the speed V1 from the change height Hc to a substrate height Ht. While the height position of the polishing surface is from the initial height H0 to the change height Hc, a polishing tape is moved at the speed Si lower than the speed Sh from the change height Hc to the substrate height Ht so as to reduce the idle feeding of the polishing tape.