A processing method of a wafer includes a modified layer forming step of positioning the focal point of a laser beam with a wavelength having transmissibility with respect to the wafer to the inside of a planned dividing line and executing irradiation along the planned dividing line to form modified layers inside and a water-soluble resin coating step of coating the front surface of the wafer with a water-soluble resin before or after the modified layer forming step. The processing method also includes a dividing step of expanding a dicing tape to divide the wafer into individual device chips together with the water-soluble resin with which the front surface of the wafer is coated and a modified layer removal step of executing plasma etching and removing the modified layers that remain at the side surfaces of the device chips in a state in which the dicing tape is expanded and the front surfaces of the individual device chips are coated with the water-soluble resin.