PURPOSE: To safely reduce pressure of a flow passage and a device without being directly operated by a worker by providing a controller controlling the actuation of a pressure regulater at the location away from the regulater.

CONSTITUTION: A controller 40 is connected to a pressure sensor 23, a pressure sensor 24 and a driving motor 33 with an electric wire, and controls the actuation of an automatic pressure reducing value main body 20 at a location which is more than several meters away from the automatic pressure reducing valve main body 20. The controller 40 actuates a pressure regulater 30 in the direction that a pressure plate 34 lowers if a worker depresses a first pressure lowering button 45. In contrast with this, when a secondary pressure lowering button 46 is depressed, the pressure regulater 30 is actuated in the direction that the pressure plate 34 rises. The controller 40 controls a driving motor 33 automatically to push the pressure plate 34 into the location where the open amount of the valve of a nozzle 28 becomes about pressure value set by the measured value of the pressure sensor 23, by setting use pressure.