The present invention provides a polyolefin resin composition which is excellent in mechanical properties and dimensional stability and is particularly excellent in heat resistance, a film which is excellent in mechanical properties, dimensional stability and heat resistance because it is obtained from the polyolefin resin composition and which is particularly excellent in meltdown properties, a macroporous membrane which is excellent in permeability and shutdown properties in addition to the above properties, and uses thereof. The polyolefin resin composition of the present invention (C) comprises 85 to 50% by mass of ultrahigh-molecular weight polyethylene (A) having a specific intrinsic viscosity and 15 to 50% by mass of a polymer (B) containing a repeating unit derived from 4-methyl-1-pentene, in 100% by mass of the polyolefin resin composition (C).