A large-sized exterior part of an automotive vehicle, injection-molded and formed of a polymer material comprises: (A) polypropylene in an amount ranging from 50 to 70 by weight %, the polypropylene containing ethylene in an amount not more than 15 weight % relative to the polypropylene and having a MFR (at 230.degree. C.) ranging from 5 to 60 g/10 min.; (B) ethylene-propylene copolymer rubber polymerized in the presence of a vanadium-based catalyst, in an amount ranging from 5 to 30 weight %, the copolymer containing propylene in an amount ranging from 20 to 40 weight % relative to the ethylene-propylene copolymer rubber and having a Mooney viscosity ML.sub.1+4 (100.degree. C.) ranging from 20 to 80; (C) ethylene-propylene copolymer rubber polymerized in the presence of a titanium-based catalyst, in an amount ranging from 5 to 45 weight %, the copolymer containing propylene in an amount ranging from 30 to 70 weight % relative to the ethylene-propylene copolymer rubber and having a Mooney viscosity ML.sub.1+4 (100.degree. C.) ranging from 20 to 75; and (D) polyethylene in an amount not more than 10 weight %, the polyethylene having a MFR (at 190.degree. C.) ranging from 5 to 50 g/10 min. The injection-molded article has an average thickness ranging from 2 to 6 mm, a flexural elastic modulus ranging from 3000 to 6000 kg/cm.sup.2, and a coefficient of linear expansion not higher than 8.times.10.sup.-5 /.degree.C.