To provide a method for processing a wafer, capable of reducing a defective and a breakage caused by a warp of the wafer, which is generated when forming a modified layer by laser beam irradiation.

A method for processing a wafer includes the steps of: forming a division starting point modified layer; forming a warp reduction modified layer, for reducing a warp generated in the wafer when forming a division starting point modified layer, in a back surface side of the inside of the wafer along a predetermined dividing line by irradiating the wafer from a back surface thereof along the predetermined dividing line with a laser beam in a state where a condensing point of the laser beam is positioned at the back surface side of the inside of the wafer after the division starting point modified layer formation step is finished; and grinding the back surface of the wafer in which the division starting point modified layer and the warp reduction modified layer are formed to remove the division starting point modified layer and the warp reduction modified layer to attain a finishing thickness while dividing the wafer from a starting point of at least the division starting point modified layer, thereby forming a plurality of chips with the finishing thickness.