PURPOSE: To stabilize the temperature of liquid to be sprayed and the water level in the thermostatic chamber of a spraying device for brine, etc., by using a closed thermostatic chamber as said therostatic chamber and then adding an automatic water level regulator to it.

CONSTITUTION: The liquid thermostatic chamber of a brine heater 3, etc., is sealed and brine is supplied from a brine tank 1 directly to said brine heater 3 through a conduit 16. This automatic water lelvel egulator 2 consists of a draft tube 2d inserted up to a brine part in the brine heater 3 and a short negative- pressure tube 2c having an opening at a negative pressure part 3a, and a prescribed amount of brine is supplied automatically from the tank 1 to the brine heater 3. Consequently, brine as much as sprayed brine is supplemented successively all the time to stabilize the flow of brine to the brine heater 3, thereby improving temperature stability.