Electro-rheological gel (ER gel) exhibits various adhesive characteristics according to the applied electric field. This characteristic is called the electro-adhesive effect (EA effect). The results of a recent study reveal that the EA effect also occurs in a vacuum. Therefore, it is expected that ER gel can be applied to a chucking or damping device in a vacuum process. However, the characteristics of ER gel in a vacuum have not been sufficiently clarified. The purpose of this study is to experimentally analyze the characteristic of ER gel in a vacuum. The performance of an ERG fixture element used for a silicon wafer in a vacuum is evaluated through shearing tests. The experimental results indicate that the ER gel demonstrates satisfactory performance in a vacuum. Moreover, the outgas released from the ER gel in a vacuum is evaluated, and the influence of the degassing time on the outgas is investigated.