An air supply device includes a plurality of bearings for rotatably supporting a shaft, a plurality of bearings for rotatably supporting an orbiting scroll, and a plurality of bearings for rotatably supporting each of a plurality of rotation constraint members that prevents rotation of the orbiting scroll about its own axis, but allows the orbiting scroll to orbit relative to a stationary scroll. A grease-filled bearing is used as each of the bearings. Each of the bearings for supporting the orbiting scroll includes two sealing materials disposed on respective sides of a plurality of rolling elements, and each of the sealing materials has an inner end held in contact with an inner ring and an outer end held in contact with an outer ring.