A resin composition comprising: 100 parts by weight of a resin component (component A) containing polylactic acid (component A-α); 0.001 to 10 parts by weight of a cyclic carbodiimide compound (component B) having one carbodiimide group and a cyclic structure represented by the following formula in which first nitrogen and second nitrogen are bonded to each other via a bonding group, wherein the number of atoms directly constituting the cyclic structure is 8 to 50; and 0.001 to 2 parts by weight of at least one antioxidant (component C) selected from the group consisting of a hindered phenol-based compound, a phosphite-based compound, a phosphonite-based compound and a thioether-based compound; in the above formula, Q is a divalent to tetravalent bonding group represented by the following formula, or; -X 3 - in the above formulas, Ar 1 and Ar 2 are each independently a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, 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 above aliphatic group, the above alicyclic group and a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, s is an integer of 0 to 10, k is an integer of 0 to 10, 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, 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, Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 may contain a hetero atom, when Q is a divalent bonding group, Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 are all divalent groups, when Q is a trivalent bonding group, one of Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 is a trivalent group, when Q is a tetravalent bonding 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 trivalent groups. 100 parts by weight of a resin component (component A) containing polylactic acid (component A-α); 0.001 to 10 parts by weight of a cyclic carbodiimide compound (component B) having one carbodiimide group and a cyclic structure represented by the following formula in which first nitrogen and second nitrogen are bonded to each other via a bonding group, wherein the number of atoms directly constituting the cyclic structure is 8 to 50; and 0.001 to 2 parts by weight of at least one antioxidant (component C) selected from the group consisting of a hindered phenol-based compound, a phosphite-based compound, a phosphonite-based compound and a thioether-based compound; in the above formula, Q is a divalent to tetravalent bonding group represented by the following formula, or; -X 3 - in the above formulas, Ar 1 and Ar 2 are each independently a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, 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 above aliphatic group, the above alicyclic group and a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, s is an integer of 0 to 10, k is an integer of 0 to 10, 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, 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, Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 may contain a hetero atom, when Q is a divalent bonding group, Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 are all divalent groups, when Q is a trivalent bonding group, one of Ar 1, Ar 2, R 1, R 2, X 1, X 2 and X 3 is a trivalent group, when Q is a tetravalent bonding 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 trivalent groups.