To fully deaerate an impregnating epoxy resin used in superconductive coils and superconductive magnets within a very short time by evacuating a sealed container while agitating and vibrating an epoxy resin in the container.

Fig. shows a desirable deaerator used in this method. A viscous liquid epoxy resin 1 (401) is placed in a container 3 in a sealed container 2. A rotary shaft 4 and impellers 5 are rotated (at 30rpm) by means of an electric motor 6. The container 2 is evacuated by aspiration through a pipe 8. An ultrasonic vibrator 8 provided on the bottom of the container 3 is actuated, whereupon the inside gas is removed by means of a vacuum pump 7 while the resin 1 is kept in a state in which it is agitated by means of the impellers 5. When the epoxy resin is deaerated by using this deaerator, the resin can be fully deaerated within several to several tens minutes compared to be conventional method wherein only the surface of the epoxy resin is deaerated, and 2-3 hours is necessary to fully deaerate the resin.