The invention aims to provide a cyclic carbodiimide compound which is useful as an end-sealing agent for polymer compounds. The cyclic carbodiimide compound is represented by the following formula (S): In the above formula, X is a divalent group or a tetravalent group represented by the following formula (i-4). Ar1 to Ar4 are each independently an aromatic group. They may be substituted by an alkyl group having 1 to 6 carbon atoms or phenyl group; alpha is -NO2, -NH2, -N=PA ra3, -N=C=O or two alpha can be combined to form bonding groups represented by the following formula (i-5), wherein Ara is phenyl, Z is oxygen atom or sulfur atom.