According to one embodiment, a polishing device includes a stage, a polishing unit, a warp suppressing unit, and an adsorbing mechanism. A semiconductor wafer is mounted onto the stage. The stage is rotatable around a first shaft. The polishing unit applies a force to and polishes a rear surface of the semiconductor wafer mounted on the stage. The warp suppressing unit applies a force to, during the polishing, an outer circumferential part of a front surface of the semiconductor wafer. The adsorbing mechanism adsorbs, during the polishing, a first region in the rear surface of the semiconductor wafer. The first region is on a center side relative to an area at which the polishing is performed.