To achieve the object described above, a shock absorber to solve the problem of the present invention includes a cover that covers an outer periphery of a cylinder which a reaction force air chamber forming member is slid ably in contact with, so that a slidable movement surface of the cylinder on which the reaction force air chamber forming member slidably moves is protected by the cover. Therefore, the slidable movement surface of the cylinder is not damaged by being hit by a flying stone or the like, an air tight property of the reaction force air chamber is maintained, and characteristics of an air spring included in the shock absorber do not change.