NOVELTY - The structure (10) has a container (2) accommodating a gas-separation tube (3) comprised with an opening (1). The gas-separation tube includes a permselective film formed on one surface of base material of a cylinder-with-base. A metal lid-shaped flange (4) is positioned in vicinity of opening of gas-separation tube, to isolate inner side and outer side of gas-separation tube during airtight state, to join container and gas-separation tube, when comparing internal diameter (D2) of gas-separation tube holder of container with outer diameter (D1) of the flange.    USE - For permselective-film type reactor, hydrogen purification machine for fuel cell, hydrogen production apparatus, and oxygen enrichment apparatus, etc.    ADVANTAGE - The damage to the gas-separation tube due to thermal stress can be avoided, when the thickness of the permselective film is thinner. The gas-separation tube accommodation structure can be designed compactly, so that the gas-separation tube accommodation structure can be positioned in limited narrowing space based on improved separability characteristic.    DETAILED DESCRIPTION - A catalyst (5) is positioned between outer peripheral surface of gas-separation tube and inner peripheral surface of container. The base material consists of ceramics. The volume of the cavity located between outer peripheral surface of gas-separation tube and inner peripheral surface of container is set to a, and the area of the permselective film is set to b, so that the ratio X is equal to adivide byb is 0.1-1. The film thickness of the permselective film is 0.05-10microns.    DESCRIPTION OF DRAWING(S) - The figure shows a sectional drawing of the gas-separation tube accommodation structure.    Opening (1)    Container (2)    Gas-separation tube (3)    Metal lid-shaped flange (4)    Catalyst (5)    Gas-separation tube accommodation structure (10)    Outer diameter of metal lid-shaped flange (D1)    Internal diameter of gas-separation tube holder of container (D2)