A resin composition comprising a polyester (component A) and a compound including a cyclic structure having only one carbodiimide group whose first nitrogen and second nitrogen are bonded together by a bond group (component B), wherein the number of atoms directly constituting the cyclic structure of the component B is 8 to 50, wherein the cyclic structure of the component B is represented by the following formula:, wherein Q is a divalent to tetravalent bond group represented by the following formula, or: -x 3 - wherein Ar 1 and Ar 2 are each independently a divalent to tetravalent aromatic group having 5 to 15 carbon atoms and may be substituted or may contain a heteroatom to form a heterocyclic structure, R 1 and R 2 are each independently a divalent to tetravalent aliphatic group having 1 to 20 carbon atoms, a divalent to tetravalent alicyclic group having 3 to 20 carbon atoms, a combination thereof, or a combination of the aliphatic group, the alicyclic group and a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, and may contain a heteroatom or a substituent, X 1 and X 2 are each independently a divalent to tetravalent aliphatic group having 1 to 20 carbon atoms, a divalent to tetravalent alicyclic group having 3 to 20 carbon atoms, a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a heteroatom or a substituent, s is an integer of 0 to 10, k is an integer of 0 to 10, with the proviso that when s or k is 2 or more, X 1 or X 2 as a recurring unit may differ from another X 1 or X 2, respectively, X 3 is a divalent to tetravalent aliphatic group having 1 to 20 carbon atoms, a divalent to tetravalent alicyclic group having 3 to 20 carbon atoms, a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a heteroatom or a substituent, with the proviso that when Q is a divalent bond group, Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 are all divalent groups, when Q is a tervalent bond group, one of Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 is a tervalent group, and when Q is a tetravalent bond group, one of Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 is a tetravalent group, or two of them are tervalent groups. wherein the number of atoms directly constituting the cyclic structure of the component B is 8 to 50, wherein the cyclic structure of the component B is represented by the following formula:, wherein Q is a divalent to tetravalent bond group represented by the following formula, or: -x 3 - wherein Ar 1 and Ar 2 are each independently a divalent to tetravalent aromatic group having 5 to 15 carbon atoms and may be substituted or may contain a heteroatom to form a heterocyclic structure, R 1 and R 2 are each independently a divalent to tetravalent aliphatic group having 1 to 20 carbon atoms, a divalent to tetravalent alicyclic group having 3 to 20 carbon atoms, a combination thereof, or a combination of the aliphatic group, the alicyclic group and a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, and may contain a heteroatom or a substituent, X 1 and X 2 are each independently a divalent to tetravalent aliphatic group having 1 to 20 carbon atoms, a divalent to tetravalent alicyclic group having 3 to 20 carbon atoms, a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a heteroatom or a substituent, s is an integer of 0 to 10, k is an integer of 0 to 10, with the proviso that when s or k is 2 or more, X 1 or X 2 as a recurring unit may differ from another X 1 or X 2, respectively, X 3 is a divalent to tetravalent aliphatic group having 1 to 20 carbon atoms, a divalent to tetravalent alicyclic group having 3 to 20 carbon atoms, a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a heteroatom or a substituent, with the proviso that when Q is a divalent bond group, Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 are all divalent groups, when Q is a tervalent bond group, one of Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 is a tervalent group, and when Q is a tetravalent bond group, one of Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 is a tetravalent group, or two of them are tervalent groups.