Provided is a lactic acid-based resin composition that comprises a lactic acid-based resin (component (A)), and an ethylene-unsaturated carboxylic acid copolymer (component (B)) and/or an ethylene-unsaturated carboxylic acid copolymer ionomer (component (C)). The lactic acid-based resin composition has good physical properties in melt and can be efficiently formed into films and laminates through casting or extrusion lamination. The paper laminates obtained through extrusion lamination with the resin composition have good moisture barrier property, and have the advantages of good antibacterial ability, good biodegradability and low combustion heat. And the moldings obtained from the resin composition of the invention have a characteristic which is excellent in impact strength. Further, the films and sheets formed of the resin composition have good low-temperature heat-sealability and hot-tack sealability, and the resin composition well serves as a sealant. The resin composition is favorable to various materials in a broad range, for example, for wrapping and packaging materials for foods, drinks, electronic appliances, medicines and cosmetics, for materials for use in agriculture, civil engineering and construction and for materials for compost, etc.