Abstract: The invention features flattening a sliced wafer in a thin disc-like form, and chamfered if necessary, through simultaneous double side grinding by passing the wafer through between paired cylindrical grinding rolls supported at both ends in bearings, and subsequently single side polishing or double side polishing the flattened wafer to obtain a polished wafer. A lapping step and an etching step in the related art thus can be dispensed with to curtail the process time. The grinding is done by simultaneous double side grinding, so that it is free from slice mark transfer due to vacuum suction of wafer to hold the wafer, or unlike a wax mounting system it does not involve complicated operation. Furthermore, instead of batch grinding, continuous grinding can be readily made. The process is thus free from working stock removal fluctuations and permits high flatness and stable thickness to be obtained by the grinding.