To provide a highly transparent thermoplastic resin composition without requiring, for example, a special molecular design or incorporation of an additive, with the refractive index of the composition being readily controllable.The highly transparent and refractive-index-controllable thermoplastic resin composition can be produced by blending a thermoplastic resin (A) containing a structural unit derived from a (meth)acrylic acid ester monomer represented by a specific chemical formula and a structural unit derived from an aromatic vinyl monomer represented by a specific chemical formula, with a thermoplastic resin (B) obtained by hydrogenating aromatic double bonds of a thermoplastic resin which contains a structural unit derived from a (meth)acrylic acid ester monomer represented by a specific chemical formula and a structural unit derived from an aromatic vinyl monomer represented by a specific chemical formula.