PURPOSE: To enable to simply and accurately control vapor amount fed to a soybean milk raw material-treating container according to use conditions.

CONSTITUTION: Soybean milk raw material is fed from a raw material tank into a soybean milk raw material-treating container. The temperature in the interior of the soybean milk raw material-treating container is set by controlling the vapor amount to be fed thereinto. The control of the vapor amount is carried out by controlling a rotation amount of a vapor amount control valve 14 while watching a temperature display in the soybean milk treating container. Since a handle provided with a dial for displaying the rotation amount is attached to the vapor amount control valve, rotation amount of the vapor control valve in adequate conditions can be known by reading the display dial. Thereafter, the rotation amount is preferably set by making it coincide with display amount of the display dial. Thereby, operation under same conditions can always be carried out without depending on skill, etc., of workers and soybean milk having uniform quality can be obtained.