An object of the present invention is to provide a curable composition that provides high hardness and can be used in adhesives and coating agents. This object can be achieved by a curable composition containing: 100 parts by weight of a reactive silyl group-containing organic polymer (A) that has a number average molecular weight of 2,000 to 6,000 and contains 1.3 to 5 reactive silyl groups per molecule; and 0 to 40 parts by weight of a plasticizer (C). This curable composition is suitable for flooring adhesives and tile adhesives, which require high hardness.