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 of an edge portion in the one silicon wafer is within an allowable angle range of a target wafer taper angle .sub.0 includes a first truing step; a first chamfer machining step; a step of determining a groove bottom diameter .sub.A of the fine grinding grindstone portion; a second truing step using a second truer taper angle .sub.2; and a second chamfer machining step. The second truer taper angle .sub.2 is made larger than the first truer taper angle .sub.1.

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 of an edge portion in the one silicon wafer is within an allowable angle range of a target wafer taper angle .sub.0 includes a first truing step; a first chamfer machining step; a step of determining a groove bottom diameter .sub.A of the fine grinding grindstone portion; a second truing step using a second truer taper angle .sub.2; and a second chamfer machining step. The second truer taper angle .sub.2 is made larger than the first truer taper angle .sub.1.