To polish semiconductor wafers smoothly and continuously.

In this device 10, a cassette installing part 14 necessary for processing wafers 28, an aligner 16, a loading stage 18, a wafer-polishing part 20, an unloading stage 22 and a cleaning and drying part 24 are installed. Then, these are connected in-line by a robot for carrying, and the like and the wafers 28 are efficiently made to flow without wastage along this line and are processed. Moreover, in the wafer-polishing part 20, a first polishing surface plate 136A and a second polishing surface plate 136B are provided side by side and when the wafers 28 with an oxide film is to be polished, the wafers 28 are polished with only the surface plate 136A and in the case of the wafers 28 with a metal film to be polished, the wafers 28 are subjected to primary polishing by the surface plate 136A, and thereafter is subjected to a secondary polishing by the surface plate 136B.