A wafer is divided into individual devices along division lines formed on the front side of the wafer. The devices are respectively formed in a plurality of regions partitioned by the division lines. A protective member is provided on the front of the wafer, and the back of the wafer is ground to a predetermined thickness. A laser beam is applied to the wafer from the back side of the wafer along the division lines with the focal point of the laser beam set inside the wafer at a position corresponding to each division line, thereby forming a plurality of modified layers inside the wafer along the division lines. The wafer is divided along the modified layers into the individual devices, and the back side of the wafer is ground to remove the modified layers and reduce the thickness of each device to the finished thickness.