To provide a processing method of a wafer in which a gettering sink effect is sustained while ensuring flexural strength.

The processing method of the wafer for imparting the gettering sink effect to the wafer having a plurality of devices formed on the surface comprises a step for forming a predetermined amount of a strained layer on the rear surface of the wafer by immersing the rear surface of the wafer into liquid mixed with abrasive grains and contained in a processing tub, and imparting an ultrasonic wave to the liquid mixed with abrasive grains so that the mixed abrasive grains act on the rear surface of the wafer.