The length of the bearing surface in the movable portion which moves linearly is larger than the length of the bearing surface in the fixed portion by the stroke of the movement. With this configuration, the bearing surface on the side of the fixed portion always opposes the bearing surface on the side of the movable portion. An air supply source is connected to the fixed portion, and a plurality of air discharge openings through which air is injected are disposed in the bearing surface of the fixed portion to constitute an air bearing. Only the side of the movable portion where the fixed portion is inserted is open. A coil is disposed on the fixed portion and a magnet is disposed on the movable portion so that a linear motor is constituted, thus providing a linear driving device. Cables and the like for supplying compressed air or power are connected to the fixed portion, not to the movable portion, thus no external pressure is applied from the cable and the like, and highly accurate operation is achieved.