A reference image of a pattern having a first pitch and projected on a sample 1 by a projector 6 is captured by a camera 5. Next, a measuring image of a pattern having a second pitch and projected on the sample 1 by the projector 6 is captured by the camera 5. Here, the second pitch of the pattern light is determined by a value calculated based on the phase resolution of the pattern light having the first pitch. Then, using the reference image thus obtained, phase coupling for the measuring image is performed. The three-dimensional shape of the sample is obtained in this manner.