To provide a thermoplastic resin compsn. which gives a molded article having a low head impact index, a high heat distortion resistance, and excellent external appearance and moldability.

This compsn. is prepd. by adding 0.01-5 pts.wt. at least one stabilizer selected from among hindered amine stabilizers (a), phosphite stabilizers (b), and hindered phenol compds. (c) and 0.05-8 pts.wt. ester lubricant (d) to 100 pts.wt. resin compsn. which comprises an acrylic ester copolymer (I) prepd. by copolymerizing an arom. vinyl compd. and a monomer copolymerizable therewith, 15-80 pts.wt. maleimide copolymer (II) prepd. by copolymerizing a maleimide monomer, an alkyl (meth)acrylate, an arom. vinyl compd., a vinyl cyanide compd., and a monomer copolymerizable therewith, and 20-85 pts.wt. graft copolymer (III) prepd. by copolymerizing a rubbery polymer (A) and a monomer mixture comprising an arom. vinyl compd., a (meth) acrylic ester, a vinyl cyanide compd., and a monomer copolymerizable therewith and in which the rubbery polymer content is 5-50 wt.%.