NOVELTY - A fluorine-containing polymer composition contains fluorine-containing polymer (A) with methylene group, and hydrosilylation reaction catalyst (B). Polymer (A) has repeating unit having methylene group in main chain and is hydrosilylated in presence of catalyst (B). Polymer (A) has carbon-carbon double bond or silicon hydride (SiH) group in one end of chain, and SiH group or carbon-carbon double bond in other end of chain.    USE - For cured material; coating agent; multilayer articles; base material integrated product; gasket for magnetic recording device; sealant (all claimed) for fuel cells and clean installation; and molded product such as O-ring, packing, sealant, roll, tube, coating, lining, gasket, diaphragm, hose, shaft seal, wall stem seal and peripheral equipment used in semiconductor manufacturing apparatus, chemical vapor deposition apparatus, dry etching apparatus, sputtering apparatus, washing apparatus, exhaust gas device, ion implantation equipment, motor vehicle such as cam-shaft seal, metallic gasket and oil hose, ship component such as valve seal and shaft seal, aircraft such as twin carburetor tube and diaphragm for sensor, rocket such as jet engine-valve seal and fuel supply hose, chemical manufacturing process such as agrochemical and pharmaceutical, photograph field such as developing machine, printing roll and coating roll, printing field such as ink tube of printer, belt of copier and scraper, foodstuffs manufacturing plant, analysis, atomic couplant apparatus, steel industries, general industries, electric component, fuel cell such as sealant between electrode and separator, and electronic component.    ADVANTAGE - The fluorine-containing polymer composition has excellent chemical resistance, solvent resistance, heat-resistant property, flame retardance, fluidity, moldability and low gas permeability. The composition provides cured material with excellent mechanical strength and rubber elasticity, and does not produce toxic substances during curing.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) cured material which is obtained from the fluorine-containing polymer composition;    (2) coating agent comprising the fluorine-containing polymer composition;    (3) multilayer articles which has a base material and a coating layer formed by the coating agent;    (4) base material integrated product which is obtained by integral molding of a molded product obtained from the fluorine-containing polymer composition on a base material by formed-in place gasket (FIPG) method or liquid injection molding (LIM) method;    (5) gasket for magnetic recording devices which contains the composition;    (6) sealant for fuel cells which comprises polymer composition;    (7) molding method of packing which involves using the polymer composition and molding by FIPG or LIM method; and    (8) fluorine-containing polymer with methylene group which has SiH group at the both terminals of the principal chain and number average molecular weight of 500-500000. The polymer is copolymer (I) having vinylidene fluoride, copolymer (II) containing tetrafluoroethylene and propylene, and/or copolymer (II) having hexafluoropropylene and ethylene.