An environmentally-friendly polylactic acid resin composition includes (A) a mixed resin including (a1) a polylactic acid (PLA) resin and (a2) a polycarbonate resin, and (B) a compatibilizer capable of forming a stereo-complex with the polylactic acid resin. According to the present invention, the polylactic acid resin composition is environmentally-friendly and has excellent appearance and improved welding impact strength, as well as improved mechanical strength and heat resistance. Accordingly, it can be used for manufacturing various molded products requiring heat resistance and mechanical strength, for example electronic parts, office machines, miscellaneous goods, and the like.