PURPOSE: To raises gas temperature which is dropped owing to pressure reduction, to shorten the length of piping up to a flow rate measuring instrument, and to make gas supply facilities compact by providing a heat collecting means on the outside surface of a housing which is provided with a pressure reducing mechanism inside.

CONSTITUTION: The pressure regulator 1 which is constituted by providing the pressure reducing mechanism 13 in the housing composed of an upper case 11 and a lower case 12 made of aluminum allow and supplies gas reduced in pressure by this pressure reducing mechanism 13 to the flow rate measuring instrument is provided with plural heat collecting plates 12d, made of aluminum alloy integrated with the lower case 12, on the back surface side of the lower case 12. Those heat collecting plates 12d are provided, specially, at the parts of an intermediate pressure chamber, an intermediate pressure passage, and a pressure reducing value 14, and outside heat can efficiently be conducted to the gas in the intermediate pressure chamber, intermediate pressure passage, and pressure reducing value 14. Consequently, the temperature of the gas dropped owing to pressure reduction rises almost up to room temperature while passing the housing. Therefore, the length of the piping between the pressure regulator and flow rate measuring instrument can be shortened.