Processing method of wafer

A processing method of a wafer for dividing, into individual device chips, the wafer on which a plurality of devices are formed on a front surface in such a manner as to be marked out by a plurality of planned dividing lines that intersect each other, the processing method comprising:

• a modified layer forming step of positioning a focal point of a laser beam with a wavelength having transmissibility with respect to the wafer to an inside of the planned dividing line and executing irradiation with the laser beam along the planned dividing line to form modified layers inside;
• 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;
• a frame supporting step of sticking a back surface of the wafer to a dicing tape and supporting an outer circumference of the dicing tape by a ring frame having an opening part that houses the wafer, before or after the modified layer forming step;
• a dividing step of expanding the dicing tape to divide the wafer into the individual device chips together with the water-soluble resin with which the front surface of the wafer is coated, in the dividing step, one of (1) the dicing tape is expanded to divide the wafer into the individual device chips before the water-soluble resin solidifies, or (2) the water-soluble resin is heated and softened in a case in which the dicing tape is expanded to divide the wafer into the individual device chips after the water-soluble resin solidifies;
• a modified layer removal step of executing plasma etching and removing the modified layers that remain at side surfaces of the device chips in a state in which the dicing tape is expanded and front surfaces of the individual device chips are coated with the water-soluble resin;
• and
• a water-soluble resin removal step of removing the water-soluble resin with which the front surfaces of the device chips are coated.