A polypropylene resin containing an α-olefinic copolymer rubber and an inorganic filler is stabilized by incorporating therein the following 6 components:

(A) a hindered phenolic compound having a molecular weight of not less than 500,
(B) a high-molecular hindered piperidine compound such as poly[{6-(1,1,3,3 - tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)-imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)-imino}],
(C) a low-molecular hindered piperidine compound such as 2-methyl-2-(2,2,6,6-tetramethyl-4-piperidyl)amino-N-(2,2,6,6-tetramethyl-4-piperidyl)-propionamide,
(D) a benzoate compound such as 2,4-di-t-butylphenyl 3,5-di-t-butyl-4-hydroxybenzoate,
(E) a phosphorous compound such as bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite, and
(F) an amide compound such as ethylenebisstearylamide. This composition may also contain a sulfur compound such as dialkyl thiodipropionate and pentaerythritol tetrakis(3-alkylthiopropionate). The composition disclosed is stable not only against heat and oxidation but also against light.