Wafer processing method

A wafer processing method comprising:

• a bonded wafer forming step of forming a bonded wafer by bonding one surface of a first wafer to one surface of a second wafer, the first wafer having a device region in which a plurality of devices are formed on the one surface, a peripheral surplus region surrounding the device region, and a chamfered peripheral edge;
• a modified layer forming step of forming an annular modified layer along a boundary of the device region and the peripheral surplus region of the first wafer by applying a laser beam having such a wavelength as to be transmitted through the first wafer to the one surface of the first wafer from another surface of the first wafer that is opposite to the one surface thereof, with a focal point of the laser beam placed at the boundary;
• a grinding step of, after the modified layer forming step, grinding the first wafer of the bonded wafer from the other surface of the first wafer to thin the first wafer to a finished thickness;
• and
• an external force exerting step of, during or after the grinding step, exerting an external force on the peripheral surplus region that is close to the peripheral edge with respect to a region in which the modified layer is formed in the modified layer forming step, to thereby facilitate separation of the peripheral surplus region.