A curable composition having good curability and adhesion comprising: (A) an reactive silicon group-containing organic polymer, (B) a titanium chelate represented by the general formula (1) or (2) and (C) a high molecular weight plasticizer having a number average molecular weight of 1,000 to 15,000. General formula (1): wherein each of n R1s is independently a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms, each of (4-n) R2s is independently hydrogen atom or a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms, each of (4-n) A1s and (4-n) A2s is independently —R3 or —OR3 where R3 is a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms, n is 1, 2 or 3. General formula (2): wherein R2, A1 and A2 are the same as defined above, R4 is a substituted or unsubstituted divalent hydrocarbon group having 1 to 20 carbon atoms.