To obtain a thermoplastic resin composition which is excellent in thermal moldability, impact resistance, flame retardance, heat resistance, and see-through properties and does not exhibit discoloration even after thermal molding by mixing a polyester resin with a polycarbonate resin and adding a pentaerythritol phosphite compound to the resultant resin mixture.

A polyester resin prepared by the polycondensation of a dicarboxylic acid component comprising terephthalic acid or its derivative and a glycol component containing at least 40 mol% 1,4-cyclohexanedimethanol is mixed with a polycarbonate resin in a wt. ratio of (90/10)-(10/90). The objective thermoplastic resin composition is prepared by adding 0.05-3 pts.wt. at least one pentaerythritol phosphite compound represented by formula I (wherein R1 and R2 are each H, alkyl, cycloalkyl or aryl), perferably one represented by formula II, to 100 pts.wt. above-prepared resin mixture.