A curable composition includes organic polymer (A) having more than one reactive silicon group on average per molecule, represented by formula (1): —SiR1aX3-a (1), wherein R1 is a substituted or unsubstituted hydrocarbon group having 1-20 carbon atoms, each X is independently a hydroxy group or a hydrolyzable group, and a is 0 or 1, and (meth)acrylate-based polymer (B) having a reactive silicon group represented by formula (2): —SiX3 (2), wherein each X is as defined for the formula (1), polymer (B) has a reactive silicon group equivalent of not less than 0.30 mmol/g, and wherein a monomer (b1) is free of a reactive silicon group, a glass transition temperature of its homopolymer is not more than 80° C., and is contained as monomer(s) constituting polymer (B) in a proportion of not less than 40 wt % per 100 wt % of total monomer.