Processing method of wafer

A processing method of a wafer having a device region on which a plurality of devices are defined by division lines on a front surface of the wafer, and an outer peripheral surplus region formed in a periphery of the device region, the processing method comprising:

• forming a separation groove having a depth corresponding to a finished thickness of the device region to be obtained after the processing, the separation groove being in a boundary between the device region and the outer peripheral surplus region on the front surface of the wafer;
• adhering a protection tape on front surfaces of the device region and the outer peripheral surplus region;
• grinding the protection tape opposed to a chuck table of a grinding apparatus, the wafer is held on the chuck table, a back surface of the wafer corresponding to the device region is ground into a thickness corresponding to the finished thickness of the device region, a thick reinforcing portion is formed on a portion corresponding to the outer peripheral surplus region, the reinforcing portion and the device region are connected to each other by the protection tape;
• transferring out the wafer which has been subjected to the grinding step from the chuck table;
• separating the reinforcing portion from the device region so that only the device region remains as the wafer;
• mounting a dicing frame on the back surface of the wafer via a dicing tape;
• and
• dividing the wafer supported by the dicing frame into the devices.