The following are observed using a camera: a first position of a small hole of a workpiece, which is fixed to a linear-and-tilting-motion stage and rotating with a rotating body, and a second position thereof different from the first position, at a first rotation angle of the rotating body; and the first position and the second position of the small hole of the workpiece at a second rotation angle different from the first rotation angle of the rotating body. A position and a tilt of the small hole are calculated from coordinates of the respective observed positions, and small hole information, which includes the position and the tilt of the small hole, is outputted.