A thermoplastic resin composition, comprising: 20 to 30 % by weight of an ABS-based graft copolymer comprising a conjugated diene-based rubber polymer having an average particle diameter of 0.25 to 0.35 pm; 2 to 10 % by weight of a rubber-modified graft copolymer comprising a rubber polymer having an average particle diameter of 0.6 to 10 μm and prepared by continuous bulk polymerization; and 65 to 75 % by weight of a matrix resin, wherein a total content of the ABS-based graft copolymer and the rubber-modified graft copolymer is 25 to 35 % by weight based on a total weight of the thermoplastic resin composition, wherein the matrix resin comprises 25 to 33 % by weight of a maleimide compound-aromatic vinyl compound copolymer and 67 to 75 % by weight of an aromatic vinyl compound-vinyl cyanide compound copolymer, being a heat-resistant styrene-based resin having a glass transition temperature of 115 to 140 °C as measured by DSC, wherein the maleimide compound-aromatic vinyl compound copolymer comprises 40 to 60 % by weight of a maleimide compound, 40 to 55 % by weight of an aromatic vinyl compound, and greater than 0 and 8 % by weight or less of a maleic anhydride to provide the glass transition temperature of 115 to 140°C as measured by DSC, wherein, when a sheet (130 mm in width and 130 mm in length) manufactured from the thermoplastic resin composition is vibration-welded to a sheet (130 mm in width and 130 mm in length) that is made of poly(methyl methacrylate) (PMMA) and comprises a vibration-welding projections on one surface thereof (under conditions of a frequency of 230 Hz, a pressure of 4707 N (480 kgf), and an amplitude of 1.2 mm), a vibration weldability calculated by Mathematical Equation 1 below is 6 or less: Vibration weldability seconds = T 2 − T 1 wherein T2 is a time required for vibration welding in a direction of 80° to a direction of a welding projections, and T1 is a time required for vibration welding in parallel with the direction of the welding projections. 20 to 30 % by weight of an ABS-based graft copolymer comprising a conjugated diene-based rubber polymer having an average particle diameter of 0.25 to 0.35 pm; 2 to 10 % by weight of a rubber-modified graft copolymer comprising a rubber polymer having an average particle diameter of 0.6 to 10 μm and prepared by continuous bulk polymerization; and 65 to 75 % by weight of a matrix resin, wherein a total content of the ABS-based graft copolymer and the rubber-modified graft copolymer is 25 to 35 % by weight based on a total weight of the thermoplastic resin composition, wherein the matrix resin comprises 25 to 33 % by weight of a maleimide compound-aromatic vinyl compound copolymer and 67 to 75 % by weight of an aromatic vinyl compound-vinyl cyanide compound copolymer, being a heat-resistant styrene-based resin having a glass transition temperature of 115 to 140 °C as measured by DSC, wherein the maleimide compound-aromatic vinyl compound copolymer comprises 40 to 60 % by weight of a maleimide compound, 40 to 55 % by weight of an aromatic vinyl compound, and greater than 0 and 8 % by weight or less of a maleic anhydride to provide the glass transition temperature of 115 to 140°C as measured by DSC, wherein, when a sheet (130 mm in width and 130 mm in length) manufactured from the thermoplastic resin composition is vibration-welded to a sheet (130 mm in width and 130 mm in length) that is made of poly(methyl methacrylate) (PMMA) and comprises a vibration-welding projections on one surface thereof (under conditions of a frequency of 230 Hz, a pressure of 4707 N (480 kgf), and an amplitude of 1.2 mm), a vibration weldability calculated by Mathematical Equation 1 below is 6 or less: Vibration weldability seconds = T 2 − T 1 wherein T2 is a time required for vibration welding in a direction of 80° to a direction of a welding projections, and T1 is a time required for vibration welding in parallel with the direction of the welding projections. wherein a total content of the ABS-based graft copolymer and the rubber-modified graft copolymer is 25 to 35 % by weight based on a total weight of the thermoplastic resin composition, wherein the matrix resin comprises 25 to 33 % by weight of a maleimide compound-aromatic vinyl compound copolymer and 67 to 75 % by weight of an aromatic vinyl compound-vinyl cyanide compound copolymer, being a heat-resistant styrene-based resin having a glass transition temperature of 115 to 140 °C as measured by DSC, wherein the maleimide compound-aromatic vinyl compound copolymer comprises 40 to 60 % by weight of a maleimide compound, 40 to 55 % by weight of an aromatic vinyl compound, and greater than 0 and 8 % by weight or less of a maleic anhydride to provide the glass transition temperature of 115 to 140°C as measured by DSC, wherein, when a sheet (130 mm in width and 130 mm in length) manufactured from the thermoplastic resin composition is vibration-welded to a sheet (130 mm in width and 130 mm in length) that is made of poly(methyl methacrylate) (PMMA) and comprises a vibration-welding projections on one surface thereof (under conditions of a frequency of 230 Hz, a pressure of 4707 N (480 kgf), and an amplitude of 1.2 mm), a vibration weldability calculated by Mathematical Equation 1 below is 6 or less: Vibration weldability seconds = T 2 − T 1 wherein T2 is a time required for vibration welding in a direction of 80° to a direction of a welding projections, and T1 is a time required for vibration welding in parallel with the direction of the welding projections.