To prevent freezing of a pressure reduction device for depressurizing and gasifying hydrogen chloric gas to supply the gas to a use point.

The pressure reduction device 10 provide on respective lines 3a, 3b, 5a, 5b through which the hydrogen chloric gas passes is stored in a container 17 together with these lines. The pressure reduction device 10 is immersed in a heat transmitting medium 18 of liquid. The heat transmitting medium 18 in the container 17 is circulated through a circulation path 25 of the circulation system 19 by driving of a circulation pump 26. The heat transmitting medium 18 to be circulated is heated by a heater 21. Heating temperature of the heat transmitting material 18 by heating of the heater 21 is controlled at the set temperature by a temperature adjuster 22 based on detected temperature of the heat transmitting material 18 to be detected by a temperature sensor 20. The freezing of the pressure reduction device 10 is prevented by compensating quantity of heat to be absorbed by the hydrogen chloric gas in accordance with evacuation of the pressure reduction device 10 by quantity of heat by a heater of the heat transmitting medium 18.