Provided is a method for identifying a disturbance component, including: when a vibration frequency included in a position deviation or a synchronization error between a tool axis and a workpiece axis is defined as fd, and a sampling frequency of a sampling period, which is a time from when a tool cuts a single tooth trace on a workpiece until the tool again cuts the same tooth trace, is defined as Fs, determining a frequency Fa of undulation in a tooth trace direction from a formula: Fa=MIN|fd−N×Fs|, where N is a natural number,
calculating a pitch of undulation in the tooth trace direction using the formula and a speed of the tool axis in a feed direction; and when the calculated pitch and a measured value of the pitch match, determining that fd is the disturbance component.