Thermoplastic resin composition

A thermoplastic resin composition comprising:

• a graft copolymer (I) obtained by graft-polymerizing a monomer mixture (B) containing an aromatic vinyl-based monomer and a vinyl cyanide-based monomer in the presence of an acryl-based rubbery polymer (A) which is obtained by copolymerizing 97 to 99.3% by weight of an acrylic acid ester-based monomer (a) and 0.7 to 3% by weight of a polyfunctional monomer (b) and has a volume average particle size of 0.10 to 0.3 μm;
• and
• a vinyl-based copolymer (II) obtained by copolymerizing at least an aromatic vinyl-based monomer and a vinyl cyanide-based monomer,
• the thermoplastic resin composition containing 30 to 70 parts by weight of the graft copolymer (I) and 30 to 70 parts by weight of the vinyl-based copolymer (II) based on 100 parts by weight of the total of the graft copolymer (I) and the vinyl-based copolymer (II),
• wherein the graft copolymer (I) satisfies the following formula (1) for the ratio of a gel swelling degree (α) of the acryl-based rubbery polymer (A) in toluene to a graft ratio (β) of the graft copolymer (I) (α)/(β)), and particles of the graft copolymer (I) are aggregated in the thermoplastic resin composition
• 0.4≤(α)/(β)≤2.0 (1).