To provide a multi-branched organic polymer having low viscosity and excellent extension property of cured material and provide a curable composition, sealing material and an adhesive containing the polymer.

The multi-branched polymer at least has a crosslinkable and hydrolyzable silyl group and the total number of the polymerization starting terminals and the polymerization stopping terminals is ≥3. The multi-branched polymer is preferably at least one kind of polymer selected from a star polymer, a star burst polymer, a comb polymer and a graft polymer. The invention further provides a curable composition containing the multi-branched organic polymer, a curable composition preferably further containing a layer silicate, a sealing material composed of the curable composition and an adhesive composed of the curable composition.