To provide a method for grinding a wafer, capable of reducing the possibility that a device is broken by a crack occurring from a notch as a starting point.

A method for grinding a wafer by grinding a back surface of the wafer to thin the wafer so as to have a predetermined thickness, the wafer including, on its surface, a device region having devices each having a plurality of bumps and an outer peripheral excessive region surrounding the device region, and having a V-shaped notch 23 indicating a crystal orientation of the wafer formed in its outer peripheral edge, includes the steps of: forming a cut groove 25 as a crack prevention portion having a depth from a surface of the wafer to a finishing thickness of the wafer in the outer peripheral excessive region of the wafer so as to be opposed to an apex of the V-shaped notch; disposing a protective material on the surface of the wafer; and holding the wafer by a chuck table via the protective material, and grinding the back surface of the wafer having the back surface exposed by using grinding means to thin the wafer so as to have the finishing thickness.