PURPOSE: To stabilize the raw material supplying amount of a bubbling-type raw material supplying apparatus.

CONSTITUTION: Separately from a main tank 10 which carries out bubbling, a liquid surface level adjusting pipe 40 is installed. Since the tank and the pipe 40 are made to communicate with each other through an orifice 42 and a ventilation pipe 43, the liquid surface level is the same in both the tank and the pipe 40 but the fluctuation of the liquid surface level following bubbling in the main tank 10 does not affect the liquid surface level adjusting pipe 40. The supplementary raw material liquid is continuously sent to the liquid surface level adjusting pipe 40 from a subtank 20 through a liquid sending pipe 23 and a liquid flow rate controller 31. The liquid surface level of the liquid surface level adjusting pipe 40 can be detected by a liquid surface level sensor 46 and since the liquid flow rate controller 31 is controlled by a controlling apparatus 32, the raw material liquid is supplemented corresponding to the consumption amount of the raw material liquid 11 in the main tank 10 and the liquid surface level is kept constant.