Abstract: A double acting cylinder actuated by air pressure having inner and outer double-wall cylinder tubes. A plurality of pairs of air pressure feed-exhaust ports of the cylinder tubes of this double acting cylinder are concentratedly provided as a pair on the outer periphery at one or opposite ends, or on an end face of the cylinder, respectively. Air communication passages for communicating a pair of feed-exhaust ports with first and second spaces of a cylinder bore can be easily changed by reversing the outer or inner cylinder tube in the axial position thereof. In this case, seal rings are changed in position as necessary, unused feed-exhaust ports are blocked by seal plugs, and only one pair of feed-exhaust ports, which are necessary are connected thereto with air pressure pipings.