To provide the grinding method of a wafer made of lithium tantalate or lithium niobate, for suppressing breakage of the wafer.

The grinding method of grinding the wafer made of the lithium niobate or lithium tantalate, the wafer having a device area where a plurality of devices are formed on the surface and an outer peripheral surplus area surrounding the device area, includes: a sticking step of sticking a protective tape to the surface of the wafer; a holding step of holding the surface of the wafer to which the protective tape has been stuck by the chuck table via the protective tape; and a grinding step of making a grinding wheel abut on the rear surface of the wafer held by the chuck table while rotating the grinding wheel having an outer diameter such that a grinding stone passes through the rotational center of the wafer and the outer peripheral edge of the grinding stone passes through the outer periphery of the device area, grinding the rear surface of the wafer corresponding to the device area to form a circular recessed part, and forming an annular projection part including the outer peripheral surplus area on the outer peripheral side of the circular recessed part.