Disclosed herein is a polypropylene-base resin composition obtained by heating at a temperature of 170 DEG C.-280 DEG C. a mixture containing a crystalline ethylene-propylene block copolymer having a specific composition, an ethylene-propylene copolymer rubber having a specific composition and viscosity, an inorganic filler having a specific particle size, and an organic peroxide, all in specified amounts. The thus-obtained polypropylene-base resin composition has high molding fluidity and are inexpensive and their moldings have excellent low-temperature impact resistance and paintability along with high stiffness. They are thus suitable for use in the production of large moldings such as automobile bumpers, fenders and body sidemembers.