The invention provides a polylactic acid-based resin having a high molecular weight, high heat resistance and an amide bond in its molecular chain, a production process and a use thereof. The polylactic acid-based resin comprises a constituting unit represented by the following formula (1) and which is obtained by allowing a polyisocyanate compound to react with a mixture comprising at least a poly (L-lactic acid) in which the percentage of the terminal functional group which is a carboxyl group exceeds 50% and a poly(D-lactic acid) in which the percentage of the terminal functional group which is a carboxyl group exceeds 50%.
