NOVELTY - An organic polymer comprises organic polymer (a-1) which has silicon group that condenses silicon compound (a-2). The organic polymer has average of greater than or equal to 1 per molecule of silicon groups.    USE - Organic polymer for curable composition (claimed) used in sealing material (e.g. for direct gradings, multi-layer glasses or working joint of building, joints of exterior materials, medical equipment sealing material, food packaging material, sizing board, coating material, primer, electroconductive material for electromagnetic wave shielding, thermal conductivity material, hot-melt material, waterproof of laminated glass end surface, motor vehicle component, electrical machinery components and machine components), adhesive agent (e.g. for interior panels, face panels, tiling, stone spreading, ceiling finishing, floor finishing, wall finishing, vehicle panels, electricity, electron and precision equipment assemblies), electrical insulation materials (e.g. electrical, electronic components materials, solar cell back surface sealing agent, insulation coating electric wire, cable material, elastic adhesive agent, contact adhesive, spray-type sealing material, crack repair material, powder coatings, casting material, medical rubber material, medical adhesive), potting agent for electric electrons, film, gasket and fluid-sealant agent molding materials and wire glass.    ADVANTAGE - The organic polymer has excellent hardenability without using organic tin type catalyst.    DETAILED DESCRIPTION - An organic polymer comprises organic polymer (a-1) which has silicon group of formula -SirR1aYb(OH)c that condenses silicon compound (a-2) of formula SiX4. The organic polymer has average of greater than or equal to 1 per molecule of silicon groups of formula -O-SiX3.    R1=1-20C hydrocarbon group or triorganosiloxy group of formula (R')3SiO-;    R'=1-20C hydrocarbon group;    Y=hydrolyzable group;    a=0-2;    b=0-1;    c=1-3; and    a+b+c=3.    An INDEPENDENT CLAIM is included for a curable composition.