A target provided to a substrate placement portion is detected by an object detection sensor at a plurality of rotation positions of the substrate placement portion. An index length which is a distance from a robot reference axis to the target in a direction perpendicular to an axial direction, or information correlated therewith, is calculated. At least one of a rotation position of a detection line about the robot reference axis and a rotation position of the substrate placement portion about a rotation axis when the target located on a line connecting the robot reference axis and the rotation axis is detected is calculated on the basis of the calculated index length or the calculated information correlated therewith. A direction in which the rotation axis is present as seen from the robot reference axis is specified on the basis of the calculated rotation position.