To provide a processing method and a processing device in a chamfering machine which can stably supply a highly precise wafer by stabilizing a chamfering shape of the outer peripheral part of the wafer and reducing occurrence of fine chipping in a chamfering part.

In the processing method, change of grinding resistance in grinding for chamfering is detected by change of the power amount of a grinding stone rotary motor 4, and grinding velocity, that is, the number of rotations of a wafer rotary motor 3 is controlled on the basis of detected change of the power amount of the grinding stone rotary motor 4. The processing device has a chamfering machine for grinding and processing the outer periphery of the rotating wafer 1 by a rotating grinding stone 2, a motor power amount detector 5 for detecting change of power amount of the grinding stone rotary motor 4 which rotates the grinding stone in grinding, and a control device 6 which controls the number of rotations of the motor 3 rotating the wafer 1 based on change of the power amount of the grinding stone rotary motor 4 detected by the motor power amount detector 5 and changes grinding speed.