A cylinder having an output member accommodated in a cylinder hole provided in a housing and moved up and down by a pressure fluid, comprising: a first valve chamber (21, 121, 221, 321, 421, 721) provided between a lower wall of the housing and the output member; a second valve chamber (23, 123, 223, 323, 423, 723) being hollowed out of the output member so as to be provided open toward the first valve chamber (21, 121, 221, 321, 421, 721); a valve rod (10c, 110c, 210c, 310c, 410c, 710c) protruding from the lower wall to be inserted into the second valve chamber (23, 123, 223, 323, 423, 723), said valve rod (10c, 110c, 210c, 310c, 410c, 710c) comprising: a valve rod passage (10d, 110d, 210d, 310d, 410d) provided open toward the second valve chamber (23, 123, 223, 323, 423, 723); and a seal section (27, 127, 227, 327,427, 727) provided on an outer peripheral wall side of the valve rod (10c, 110c, 210c, 310c, 410c, 710c) or an inner peripheral wall side (10e, 110e, 210e, 310e, 410e) of the second valve chamber (23, 123, 223, 323, 423, 723) between the valve rod (10c, 110c, 210c, 310c, 410c, 710c) and the second valve chamber (23, 123, 223, 323, 423, 723), characterized in that a compressed air flow passage formed between the first valve chamber (21, 121, 221, 321, 421, 721) and the second valve chamber (23, 123, 223, 323, 423, 723) is configured so as to have a close region sealed by the seal section (27, 127, 227, 327, 427, 727) and an open region released from sealing when the valve rod (10c, 110c, 210c, 310c, 410c, 710c) and the second valve chamber (23, 123, 223, 323, 423, 723) move relative to each other, wherein compressed air is supplied from one end of the compressed air flow passage, and the other end of the compressed air flow passage is open to an outside air. a first valve chamber (21, 121, 221, 321, 421, 721) provided between a lower wall of the housing and the output member; a second valve chamber (23, 123, 223, 323, 423, 723) being hollowed out of the output member so as to be provided open toward the first valve chamber (21, 121, 221, 321, 421, 721); a valve rod (10c, 110c, 210c, 310c, 410c, 710c) protruding from the lower wall to be inserted into the second valve chamber (23, 123, 223, 323, 423, 723), a valve rod passage (10d, 110d, 210d, 310d, 410d) provided open toward the second valve chamber (23, 123, 223, 323, 423, 723); and a seal section (27, 127, 227, 327,427, 727) provided on an outer peripheral wall side of the valve rod (10c, 110c, 210c, 310c, 410c, 710c) or an inner peripheral wall side (10e, 110e, 210e, 310e, 410e) of the second valve chamber (23, 123, 223, 323, 423, 723) between the valve rod (10c, 110c, 210c, 310c, 410c, 710c) and the second valve chamber (23, 123, 223, 323, 423, 723), characterized in that a compressed air flow passage formed between the first valve chamber (21, 121, 221, 321, 421, 721) and the second valve chamber (23, 123, 223, 323, 423, 723) is configured so as to have a close region sealed by the seal section (27, 127, 227, 327, 427, 727) and an open region released from sealing when the valve rod (10c, 110c, 210c, 310c, 410c, 710c) and the second valve chamber (23, 123, 223, 323, 423, 723) move relative to each other, wherein compressed air is supplied from one end of the compressed air flow passage, and the other end of the compressed air flow passage is open to an outside air.