To provide a siloxane type curable composition useful as a coating material, a heat-resistant material, an optical material, an insulation material and the like, and particularly giving a cured product excellent in heat resistance.

The curable siloxane composition contains (A) a siloxane compound that is an addition reaction product of (a1) a cyclosiloxane compound having two or more hydrogen atoms bonded to silicon atoms in one molecule and (a2) a cyclosiloxane having two or more alkenyl groups in one molecule and that has two or more hydrogen atoms on an average bonded to silicon atoms in one molecule and has alkenyl groups contained in one molecule by less than two on an average, (B) a siloxane compound that is an addition reaction product of (b1) a cyclosiloxane compound having two or more hydrogen atoms bonded to silicon atoms in one molecule and (b2) a cyclosiloxane having two or more alkenyl groups in one molecule and that has two or more alkenyl groups on an average in one molecule and has hydrogen atoms less than two on an average which are bonded to silicon atoms, which are contained in one molecule, and (C) a hydrosilylation reaction catalyst.