A polyolefin resin composition (I) comprising: (A) 99.9 to 80 wt.% propylene (co)polymer in which (a) the melt flow rate (MFR) is 0.1 to 200 g/10 min, (b) the mesopentad content [mmmm] in the components insoluble in xylene at ordinary temperature (25°C) is 97.0% or higher, and (c) the content of the components soluble in xylene at ordinary temperature (25°C) is 4 to 50 wt.%; and (B) 0.1 to 20 wt.% copolymer comprising an isotactic propylene chain and, graft−bonded and/or block−bonded thereto, a copolymer chain comprising units of two or more members selected among ethylene, C<sb>3−20</sb> &agr;−olefins, cycloolefins, and aromatic vinyl monomers. It has significantly improved impact strength while retaining high rigidity. It has an excellent balance among material properties.
