To obtain injection molded objects having biodegradability and excellent flame retardance and mechanical strength, the injection molded object includes a lactic acid based resin; and a metal hydroxide in a ratio of 5 to 40 mass parts per 100 mass parts of the lactic acid based resin. The metal hydroxide is surface-treated, and Na2O (w-Na2O) present on a surface of grains of the metal hydroxide is 0.1 mass % or less based on the total mass of the metal hydroxide. Preferably, the injection molded object contains an aliphatic polyester other than the lactic acid based resin or an aromatic-aliphatic polyester in a ratio of 20 to 80 mass parts per 100 mass parts of the lactic acid based resin.