A processing method of a wafer in which a modified layer is formed inside the wafer. In the processing method, irradiation with a first laser beam is executed from a back surface side of the wafer and the modified layer is formed inside the wafer. Then, irradiation with a second laser beam is executed with the focal point thereof positioned to the inside or the front surface of the wafer and reflected light is imaged by an imaging unit. Furthermore, a processing state of the wafer is determined on the basis of a taken image. The second laser beam is shaped in such a manner that a sectional shape thereof in a surface perpendicular to a traveling direction thereof becomes asymmetric across the modified layer.