A hydrogen gas separator fixing structure includes a gas separator having a support and a membrane provided on at least one surface of the support, which membrane contains a first metal capable of separating hydrogen gas from a hydrogen-containing gas, a metal flange connected to at least one open end of the gas separator, a bonding layer containing a second metal, provided at the portion at which the gas separator and the metal flange are connected to each other and on the surface of the gas separation membrane side of the portion, a packing provided on the bonding layer, and a ring-shaped metal member capable of fixing the packing by pressing, provided so that at least part thereof is in contact with the bonding layer, wherein the bonding layer is provided by a heat treatment conducted at a temperature lower than the melting point of the second metal.