A technique to improve the stress measurement from a Debye–Scherrer ring (D–S ring) is reported. In a previous work, the authors reported a technique to calculate stress from the Fourier series of the normal strain of a D–S ring. That technique, similar to the cosα method that came before it, is inaccurate when the grain size of the specimen is relatively large. To cope with this problem, the authors propose using the oscillation of the X-ray incident angle. The present study demonstrates this technique to improve the stress measurement.