A process for producing polypropylene resin composition, which comprises heating at 170 to 280°C a composition containing specific amounts of a crystalline ethylene/propylene block copolymer of a specific formulation, an ethylene/ propylene copolymer rubber of a specific formulation and a specific viscosity, an inorganic filler of a specific particle size, and an organic peroxide. The obtained polypropylene resin composition is excellent in low-temperature impact strength and mold flowability, has good coatability and high rigidity, and is inexpensive, thus being suited for use as large-sized moldings such as bumpers, fenders, side molds, etc. of automobiles.