In conventional examples, when both upper and lower surfaces of a sheet-like workpiece such as a silicon wafer are flattened at the same time, a double-side machining apparatus such as a double-side polishing apparatus or a double-side lapping apparatus is used. For example, in the double-side polishing apparatus, a discoid planetary gear called a carrier is arranged between upper and lower turntables each having a polishing pad made of urethane foam or non-woven fabric attached thereto. The workpiece is inserted into and held in a holding hole of this carrier, and the carrier rotates or revolves by mutually rotating a sun gear and an internal gear which engage with the carrier. The upper and lower surfaces of workpiece are simultaneously polished by the rotation, the revolution, the rotation of the upper and lower turntables, and sliding on the workpiece. Further, to efficiently perform polishing, polishing slurry is supplied from a plurality of holes provided in the upper turntable during the double-side polishing.
Furthermore, the upper turntable includes a mechanism which moves up and down, the upper turntable is set at an upper position, and then the carrier is set on the lower turntable, or the workpiece is set in the set carrier. As to the setting of the workpiece into the carrier, there are a case where an operator manually performs loading into a workpiece holding hole of the carrier and a case where an automatic handling apparatus is used for loading. After the workpiece is loaded in this manner, the upper turntable moves down, and the workpiece and the carrier are sandwiched between the upper and lower turntables. Moreover, the workpiece is polished by the rotation and the revolution of the carrier which are realized by the rotation of the upper and lower turntables and the rotation of the internal gear and the sun gear while supplying the polishing slurry.