In the field of soft robotics, researchers and developers are exploring the use of flexible materials, such as silicone rubber, to create robots with pliable bodies. To create a three-dimensional structure using these materials, a common method is to use molding, where liquid rubber is poured into a mold and cured. To prevent molding defects, it is effective method to degas the mold by vacuuming. However, in a vacuum chamber, the position of both the mold and the liquid rubber inlet cannot be modified. Therefore, the molded shape and the rubber inlet and outlet points have to be carefully designed, resulting in lower efficiency of soft robot prototyping. To address this problem, we developed an invacuum molding system where the silicone rubber inlet can be manipulated from the outside of the vacuum chamber. In this paper, we evaluated the developed molding system and demonstrated its effectiveness in preventing molding defects.