A processing method for a wafer having a plurality of streets inclined at 45° relative to a cleavage direction including a laser processing step of positioning a focusing point of a laser beam with a wavelength as to be transmitted through the wafer in the inside of the wafer, and applying the laser beam along the streets to form a plurality of modified layers, overlapping with one another in the wafer thickness direction, inside the wafer along each of the streets. In the laser processing step, m modified layers (m is a natural number not less than n·√2) are formed overlapping with one another in the wafer thickness direction, where n (n is a natural number) is the number of modified layers needing to be formed overlapping with one another in a wafer thickness direction when dividing a wafer having a plurality of streets parallel to a cleavage direction.