In a wafer processing method, a modified layer is formed inside a wafer along planned dividing lines by irradiating the wafer with a laser beam with such a wavelength as to be transmitted through the wafer from the back surface side of the wafer along the dividing lines. A first modified layer is formed near the back surface of the wafer by irradiating the wafer with the light focal point of the laser beam positioned near the back surface of the wafer. The wafer is then irradiated with the light focal point of the laser beam positioned on the front surface side. Then plural second modified layers are formed in a multi-layering manner with sequential movement of the light focal point toward an area leading to the first modified layer. The wafer is divided into individual devices along the dividing lines by applying an external force to the wafer.