Method of helical chamfer machining silicon wafer

Provided is a method of chamfer machining a silicon wafer which makes it possible to increase the number of machining operations that can be performed using a chamfering wheel used for helical chamfer machining in the case of obtaining a small finished wafer taper angle. The method in which helical chamfer machining is performed so that the finished wafer taper angle θ of an edge portion in the one silicon wafer is within an allowable angle range of a target wafer taper angle θ0 includes a first truing step; a first chamfer machining step; a step of determining a groove bottom diameter ϕA of the fine grinding grindstone portion; a second truing step using a second truer taper angle α2; and a second chamfer machining step. The second truer taper angle α2 is made larger than the first truer taper angle α1.