An optical device wafer processing method including a protective plate attaching step of attaching a transparent protective plate through a double-sided adhesive tape to the front side of a sapphire substrate constituting an optical device wafer, the double-sided adhesive tape being composed of a sheet capable of blocking ultraviolet radiation and adhesive layers formed on both sides of the sheet, wherein the adhesive force of each adhesive layer can be reduced by applying ultraviolet radiation; a sapphire substrate grinding step of grinding the back side of the sapphire substrate; a modified layer forming step of applying a laser beam to the sapphire substrate from the back side thereof to thereby form a modified layer in the sapphire substrate along each street; a protective plate removing step of removing the protective plate in the condition where the double-sided adhesive tape is left on the sapphire substrate; and a wafer dividing step of breaking the sapphire substrate along each street where the modified layer is formed, thus dividing the optical device wafer into individual optical devices in the condition where the double-sided adhesive tape is left on the sapphire substrate.