A measuring member is connected with the workpiece to be measured, whose configunation is measured by moving the measuring member. One support of the measuring instrument is sustained by a guide-rail, its position is adjustable along X-axis and Z-axis. Another support is only movable along a guide-rail in one direction. The position of a sliding guide-rail set up between the supports is adjustalde along X-axis and Z-axis through a position-adjusting mechanism mounted on the connecting part between the sliding guide-rail and the supports. The sliding guide-rail adjusting in this way cannot move along the moving direction of the slide block, when the adjusting member mounted on the sliding guide-rail closly contacts the bearing surface of the supporting member. |