Abstract: One of the images of an object captured by at least three cameras is defined as a basic image, and a basic backprojection line is defined which passes through a feature point in the basic image corresponding to a noted three-dimensional feature point on the object and the optical center of the camera that captured the basic image. Reference backprojection lines are defined with respect to respective feature points on an epipolar line, obtained by projecting the basic backprojection line onto the image by each of the other cameras, and the optical center of said each camera. The coordinates of intersection points of the basic backprojection line and the reference backprojection lines are calculated and the number of the reference backprojection lines intersecting at each intersection point on the basic backprojection line is counted. The point having the maximum number of intersections is determined to be the position of the noted three-dimensional feature point.