In this work, a feasibility study has been conducted to determine if GHTA (Gas Hollow Tungsten Arc) method can be used for the welding in space. As previously described, the test for GHTA welding of stainless steel without filler wire has been successfully performed in a simulated space environment, produced by the parabolic flight of aircraft. In this paper, melt-run welding tests and butt welding tests on stainless steels for GHTA welding with filler wire have been conducted in a vacuum chamber using a developed compact wire feeder. The results are summarized as follows. (1) The developed compact wire feeder makes it possible to add the filler metal to GHTA weld pool smoothly in a vacuum. (2) A metal vapor plume is formed on the molten pool in GHTA welding and it grows brightly with increase of arc current. (3) The penetration depth in GHTA welding becomes shallow with increase of filler metal, as well as that in GTA welding under the atmospheric pressure. (4) The butt joint welded by the GHTA method of filler wire addition has no defect and it has enough strength.