NOVELTY - A hydrogen-permeation separation thin film contains zirconium-titanium-nickel-cobalt-niobium alloy including (in atomic%) zirconium (0.5-20), titanium (15-48), nickel (10-43), cobalt (0.5-25), and remainder of niobium (19-42) and unavoidable impurity. The alloy has a structure in which solid solution of intermetallic compound (nickel(cobalt)-titanium(zirconium, niobium)), and fine grain of niobium group solid solution alloy including titanium, zirconium, nickel and cobalt, are dispersed.    USE - Hydrogen-permeation separation thin film is used for chemical reactors including hydrogen refiner used for purifying hydrogen used as fuel for battery and gas turbine, and for chemical reactions such as steam reforming process of hydrocarbon and hydrogenation/dehydrogenation processes (conversion reaction of benzene to cyclohexane).    ADVANTAGE - The hydrogen-permeation separation thin film has excellent mechanical strength, and hydrogen-permeation separation performance, which is maintained for long period of time.    DETAILED DESCRIPTION - A hydrogen-permeation separation thin film contains zirconium-titanium-nickel-cobalt-niobium alloy including (in atomic%) zirconium (0.5-20), titanium (15-48), nickel (10-43), cobalt (0.5-25), and remainder of niobium (19-42) and unavoidable impurity. The total content of zirconium and titanium is 23-52 atomic%, the total content of nickel and cobalt is 22-48 atomic%, and ratio of cobalt and nickel is less than 1. The alloy has a structure in which solid solution of intermetallic compound (nickel(cobalt)-titanium(zirconium, niobium)), and fine grain of niobium group solid solution alloy including titanium, zirconium, nickel and cobalt, are dispersed. The intermetallic compound is formed by substituting a portion of nickel by cobalt, and a portion of titanium by zirconium and niobium. The refining heat processed casting foil material of zirconium-titanium-nickel-cobalt-niobium alloy having thickness of 0.07 mm formed by chill roll method, is used.