To easily mount a decompression mechanism to close a door on an existing vehicle by providing a pressure switching part which is arranged on a downstream side of the branched position of a door closing piping and on the upstream side of each door closing device, and in which either of a non- decompression piping or a decompression piping is switched according to the pressure command.

Each door 1 provided on each side part of a rolling stock 21 is opened/closed by each door closing device 2. The compressed air generated by a pressurized fluid source 4 is fed to a pressure switching part 3, and at the same time fed to other connected rolling stocks. The pressure switching part 3 comprises a piping part to pass the compressed air as it is and a piping part to decompress the pressure and pass the decompressed air in a selecting manner. The output of the pressure switching part 3 is fed to each door closing device 2 through a door closing piping 7. An end part of the door closing piping 7 rises along a side wall inside the vehicle body from a floor in the vicinity of each door 1, and connected to the door closing device 2 stored in a hole-free part of the door 1.