To provide a chemical mechanical polishing (CMP) method capable of preventing a wafer from being cracked or getting chipped, even for a face to be polished where a step difference of unevenness of the face to be polished is 0.3 to 2.0 times a board thickness.

The board polishing method, when chemical mechanical polishing the face to be polished with the uneven level differences of the face about 0.3 to 1.0 times or more of the board thickness, polishes the face to be polished by pressurizing means (pressurizing unit) 17 by setting initial polishing processing pressure to be lower than an ordinary polishing processing pressure setting value for a predetermined time, and then switches it to the ordinary polishing processing pressure set value for polishing up to a final point.