Provided an inspection method for a rotating electric machine, including: a first step of acquiring a first image by imaging a pattern formed on an outer peripheral surface of a retaining ring over an entire circumference of the retaining ring with use of an image pickup element mounted to a non-rotating portion of the rotating electric machine under a state in which the retaining ring is rotated; a second step of acquiring a second image by imaging the pattern over the entire circumference of the retaining ring with use of the image pickup element under the state in which the retaining ring is rotated, the second step being executed after the first step with an operation of the rotating electric machine interposed; and a third step of acquiring a distortion distribution of the retaining ring based on the first image and the second image.