To provide not only an injection device for pressurizing gelling constituted so as to shorten the defoaming time of a resin, excellent in defoaming capacity, enhanced in production efficiency and also suitable for the production of a large-sized product but also an epoxy resin cast product of stable quality excellent in electric insulating capacity, mechanical strength and the like.

A high speed stirrer 31 is constituted so as to mix/stirr the constituent material of the resin charged in a stirring container 311 by rotating a screw shaft 312 at a high speed. A membrane treatment type vacuum stirring and defoaming machine 32 is constituted so as to bring the resin charged in a stirring container 321 to a membrane state by utilizing the centrifugal force by virtue of the rotation of stirring blades 323 to continuously perform vacuum defoaming treatment. An injection pipe 33 having a double structure for injecting the resin in the mold installed in the vacuum chamber is constituted of a fixed pipe 331 capable of holding the inside of the mold to a vacuum state and the flexible hose 332 installed in the pipe 331.