An LED wafer is formed from a sapphire substrate having a front side. A plurality of crossing division lines are formed on the front side of the sapphire substrate to thereby define a plurality of separate regions where a plurality of LEDs are respectively formed. An LED wafer processing method includes preparing a V-blade having an annular cutting edge whose outer circumferential portion has a V-shaped cross section, rotatably mounting the V-blade in a cutting unit, holding the LED wafer on a holding table with the back side of the LED wafer exposed upward, and then relatively moving the cutting unit and the holding table to form a chamfered portion on the back side of the LED wafer along an area corresponding to each division line formed on the front side of the LED wafer.