[en] The TJ-2 HELIAC device is a stellarator proposed for the construction in Madrid by the Spanish Euratom-Ciemat Association. It is a medium size HELIAC axis stellarator with four periods, a major radius of 1.5 m, a toroidal magnetic field up to 1T, and a duty cycle up to 1 s every 5 min. The parameters of the TJ-2 machine are given. The vacuum vessel (VV) is an independent component fixed on the machine supports. It is formed to follow the shape of plasma. The VV is composed of 32 sectors and 32 rings, which are made of AISI 304 LN stainless steel to assure very low magnetic permeability. The construction of the VV is outlined. The method of suspending the VV with four suports is explained. Because of the symmetry, a three-dimensional FEM model was made for a quarter of the whole structure. The vacuum vessel element model, the results of the linear static analysis and the instability analysis are reported. Under the operating conditions, the mechanical behavior of the VV is fully satisfactory for both stress and displacement requirements. (K.I.)