PURPOSE: To control efficiently the viscosity of a raw material with high precision by providing a means for measuring the viscosity and temp. of the raw material in the deaeration of the raw material in a tank.

CONSTITUTION: A raw material 4 is thrown into a tank 3 by opening a valve 5, and the valve 5 is closed. A motor 1 is started by an operating panel 8 to rotate an agitator 6 at a constant speed, and a vacuum pump is started by opening a vacuum solenoid valve 10. The raw material 4 is agitated in the evacuated tank 3, and the detected signals of a temp. sensor 9 and a viscosity sensor 15 are inputted to an arithmetic processing/controlling unit 16. The temp. of raw material at each time is indicated on a temp. indicator 12 by the unit 16 in accordance with the detected signal of the temp. sensor 9. The torque and viscosity are also indicated respectively on a torque indicator 13 and on a viscosity indicator 14 in accordance with the detected signal of the viscosity sensor 15. The viscosity of the raw material at a specified time can be recognized in this way.