A supporting device (300) for supporting a guide rail (200) for guiding a movable member subjected to relative displacement in relation to the base table (3). The supporting device includes, base bodies (410, 510) engaged onto the base table (3) and carrying the guide rail (200), and holding section (440, 530) for holding the guide rail (200) intervening between the guide rail (200) in the state where the guide rail is carried by the base bodies (410, 510). The holding section (440, 530) supports the guide rail (200) in the state where it can move swingingly. A change in the posture or position of the base bodies (410, 510) is offset with a swinging movement by the holding section, and does not affect the guide rail. As a result, excessive force is not applied on the guide rail, so that the form of the guide rail is maintained.