In a method for thinning a semiconductor wafer by grinding a back surface of the semiconductor wafer in which semiconductor devices 2 are formed on its surface, the surface of the semiconductor wafer 1 is adhered to a support 4 via an adhesive layer 3, the back surface of the semiconductor wafer is ground while holding the support, and then the thinned semiconductor wafer is released from the support. Preferably, a semiconductor wafer is used as the support, a thermal release double-sided adhesive sheet is used as the adhesive layer, and they are separated by heating after grinding. Thus, there are provided a method for thinning a semiconductor wafer, which enables production of semiconductor wafers having a thickness of about 120 m or less without generating breakage such as cracking or chipping during the processing step and so forth as much as possible at a low cost, and a semiconductor wafer thinned further compared with conventional products in spite of a large diameter of 6 inches (150 mm) or more.