A polylactic acid resin composition containing (A) a polylactic acid resin, (B) a plasticizer, (C) an organic crystal nucleating agent, and (D) an acrylic/styrene copolymer having an epoxy group, wherein the above (B) plasticizer is an ester compound having two or more ester groups in the molecule, wherein the ester compound contains one or more members selected from the group consisting of an ester compound in which at least one kind of the alcohol component constituting the ester compound is an alcohol reacted with an alkylene oxide having from 2 to 3 carbon atoms in an amount of from 0.5 to 5 mol on average, per one hydroxyl group, and an ester compound represented by formula (I), and wherein the above (D) acrylic/styrene copolymer having an epoxy group is from 0.1 to 0.9 parts by mass, based on 100 parts by mass of (A) the polylactic acid resin. The polylactic acid resin composition of the present invention can be suitably used in various applications such as wrapping materials for food containers, daily sundries, and household electric appliances, trays for industrial parts, and the like.