Wafer processing method

A wafer processing method for processing a wafer with devices formed in regions on a side of a front surface of the wafer, the regions being defined by first scheduled division lines and second scheduled division lines that intersect the first scheduled division lines, comprising:

• a protective member bonding step of bonding a protective member on the side of the front surface of the wafer,
• a first modified layer forming step of irradiating a laser beam, the laser beam having transmissivity through the wafer, from a side of a back surface of the wafer along the first scheduled division lines and the second scheduled division lines with a focal point of the laser beam being set at a height leveled with a height of a first region located inside the wafer, the wafer being held by a chuck table via the protective member, on the side of the front surface of the wafer, whereby first modified layers are formed in the first region,
• a second modified layer forming step of, after conducting the first modified layer forming step, irradiating the laser beam from the side of the back surface of the wafer along the first scheduled division lines and the second scheduled division lines with the focal point of the laser beam being set at a height leveled with a height of a second region located inside the wafer on the side of the back surface of the wafer, whereby second modified layers are formed in the second region and cracks are also formed extending from the front surface to the back surface of the wafer to divide the wafer along the first scheduled division lines and the second scheduled division lines, and
• a grinding step of, after conducting the second modified layer forming step, grinding the wafer on the side of the back surface of the wafer to thin the wafer to a predetermined thickness.