To provide an air cylinder controlling abnormal high speed operation of a cylinder rod mechanically at the time of operation start when a cylinder body exists under the atmospheric pressure.

To a cylinder body 1a a pair of cylinder brakes 9, 9a are continuously provided. A brake shoe 13 is accommodated in an air chamber 14 on one side for a piston 12 into which a cylinder rod 1b is inserted, while a coil spring 16 which increases force of the piston 12 is accommodated in an air chamber 15 on the other side in order to operate the brake shoe 13. Flow control valves with check valves 20, 20a are connected to an air supply opening of the air chamber 14. One of the valves 20, 20a is connected to an inlet of the cylinder body 1a, and the other is connect to an outlet thereof. A flow characteristic of the flow control valve 20 is determined to retain a certain degree of air in the air chamber 14 at the time of first forward operation so as to keep a position where the brake shoe 13 becomes non-operative until the end of successive backward operation. The flow control valve 20a is determined for air in the air chamber 14 at the time of first backward operation keeping 2 position where the brake shoe 13 becomes non-operative until the end of successive forward operation.