A thermoplastic resin composition including at least (1) a heat-treated composition obtained by heat-treating dynamically a specific polypropylene and an olefin copolymer rubber in the presence of an organic peroxide and a crosslinking agent and (2) a specified polypropylene. In addition, an inorganic filler can be added to the thermoplastic resin composition. These compositions are superior in mechanical properties such as flexural modulus, thermal rigidity resistance and impact resistance, and can be suitably used as materials for home electric parts and the like.