A method for slicing an ingot may improve nanotopography at a surface of a wafer. In the method, an ingot is sliced into a plurality of wafers via a slurry while slurry is supplied to a moving wire. A first wire to form a first slicing portion at the wafer firstly slices one side of the ingot. A second wire secondly slices the remaining portion of the ingot to form a second slicing portion continued from the first slicing portion, wherein the first wire has a smaller diameter than that of the second wire.