PURPOSE: To improve accuracy of measurement by lowering dispersion of calculation of an image position on an optical cutting line and to simplify a control circuit for moving a two-dimensional image pickup sensor and for picking up image data.

CONSTITUTION: Measurement of a three-dimensional shape is carried out by an optical cutting method by using a CCD image-pickup sensor 12 having a pixel integrated body in which a plurality of pixels are aligned in the directions of orthogonal two axes. A micro-movement control device 4 conveys the image pickup sensor 12 by a prescribed small amount of distance and a video camera 3 having the image-pickup sensor 12 picks up an optical cutting line on the surface of an object to be measured at a plurality of points. A data-processing device 5 calculates a centroid point of the optical cutting line on the basis of data of light intensity of each pixel in the obtained image data and data of position of the image-pickup sensor 12. The conveyance of the image-pickup sensor 12 and picking up of the image data are controlled based on a vertical synchronizing signal from the video camera.