NOVELTY - A gear-type hydrogen permeable palladium or palladium alloy film is formed on surface of hydrogen separator by chemical plating and/or electroplating using a gear-type porous ceramic as a matrix. The gear-type porous ceramics matrix has external diameter of 20-50 mm, internal diameter of 10-25 mm, number of teeth of 15-30, teeth height of 3-8 mm and porosity of 25-40%.    USE - Gear-type hydrogen permeable palladium or palladium alloy film is used for hydrogen separator (claimed).    ADVANTAGE - The gear-type hydrogen permeable palladium or palladium alloy film has high surface area. The hydrogen separator comprising the alloy film is compact and has high efficiency.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) preparation of gear-type hydrogen permeable palladium or palladium alloy film, which involves making two ends of the porous ceramic into tubular shape without gear teeth, plating layer of palladium film on ceramic matrix surface by chemical plating using plating solution (A), or depositing metal other than platinum by chemical plating or electroplating, forming palladium alloy film by alloying process. The palladium alloy film is a palladium-silver film, which is formed using silver chemical plating solution, or a palladium-silver-copper film, which is formed using copper plating solution and silver plating solution. The silver chemical plating solution comprises (in g/L) silver nitrate (2-10), ethylenediaminetetraacetic acid disodium salt (20-50) and aqueous ammonia (300-600 ml/L). The copper plating solution comprises copper sulfate (5-15), potassium-sodium tartrate tetrahydrate (40-50) and sodium hydroxide (5-20), or copper sulfate (150-200), sulfuric acid (50-70), chloridion (20-80), polyethylene glycol (0.05-0.1) and ethylene thiourea (0.2-0.7). The silver plating solution comprises silver nitrate (60), ammonium thiosulfate (200-260), potassium pyrosulfate (90-110) and boric acid (25-35). The plating solution (A) comprises palladium(II) chloride (2-6), ethylenediaminetetraacetic acid disodium salt (40-80) and aqueous ammonia (100-400). The reducing agent is hydrazine solution; and    (2) hydrogen separator, which is obtained by sealing the two ends of gear-type hydrogen permeation palladium or palladium alloy film by ferrule method using graphite as sealing material, and sealing one end by ferrule plug or connecting with helical metal tube and metal bellows.